Quick Overview

Most AI assistants were built for one surface and bolted onto the rest. The web app is great, the mobile app is an afterthought, and whatever context you built up on your laptop does not follow you to your phone. This guide covers the 10 best AI assistants that actually work across your devices, ranked by how well they maintain context, capability, and consistency wherever you open them.

Top 10 Cross-Device AI Assistants Shortlist

• Vellum: A personal AI assistant available on desktop, iOS, web, CLI, Slack, and Telegram, with the same persistent memory shared across every surface.
• ChatGPT: A general-purpose AI assistant available on web, iOS, Android, Mac, and Windows, with memory that syncs across sessions.
• Claude: An AI assistant with strong reasoning and writing capabilities available on web, iOS, Android, and Mac desktop.
• Perplexity: A search-first AI assistant available on web, iOS, Android, and Mac with a consistent experience across surfaces.
• Google Gemini: Google's AI assistant available on web, iOS, and Android, with deep integration across Google Workspace tools.
• Microsoft Copilot: Microsoft's AI assistant available on Windows, iOS, Android, web, and Edge, with integration into Microsoft 365 apps.

Why I Wrote This

I use an AI assistant across five different surfaces every day: desktop, phone, web, Slack, and Telegram. What I noticed over time is that most tools that call themselves AI assistants were really designed for one surface and extended to the others as an afterthought. The AI that worked well on web dropped context on mobile. The one that was good on desktop had a limited phone experience. And almost none of them carried useful memory from one surface to another. Cross-device continuity is much harder than it looks, and very few tools get it right. This guide is about which ones actually do.

What Is a Cross-Device AI Assistant?

A cross-device AI assistant is a personal AI that maintains consistent capability and context regardless of which device or surface you are using. That means the same underlying memory, the same quality of response, and the same ability to take actions whether you are on your laptop, your phone, or a browser tab at someone else's desk. The conversational AI category is growing rapidly, with demand driven by users who expect AI to be available anywhere they are, not just on the device they happen to be at [1]. According to Microsoft's 2024 Work Trend Index, 75 percent of knowledge workers now use AI tools as part of their daily workflow [4], and a growing share expect those tools to follow them across devices without losing context.

Key 2026 Trends in Cross-Device AI Assistants

• AI assistants have moved from single-surface web apps to multi-platform products. Every major AI assistant now ships native mobile apps, and several have standalone desktop clients for Mac and Windows. The expectation has shifted: an AI that only works in a browser tab is no longer a full product.
• Apple Intelligence launched in October 2024 across iPhone, iPad, and Mac, bringing on-device AI to hundreds of millions of Apple users at no additional cost [2]. This raised the bar for what users expect from AI built into their operating system.
• Cross-device memory has become a differentiator. ChatGPT, Claude, and Vellum all now offer memory that persists across sessions. The quality of that memory, and whether it is genuinely shared across every surface rather than just stored in a central account, varies significantly between products.
• McKinsey's 2025 Superagency in the Workplace report found that 92 percent of companies plan to increase AI investment over the next three years [3], with personal productivity use cases on mobile and desktop among the highest-growth segments.
• The gap between AI on desktop and AI on mobile is narrowing, but it has not closed. Most tools have parity on basic chat. Fewer have parity on memory, actions, and integrations. That gap is what separates a genuine cross-device assistant from a mobile app that happens to share a login with the web version.

Why Most AI Assistants Don't Actually Work Across Devices

• The mobile app is an afterthought. Many AI tools built their desktop or web product first and shipped a stripped-down mobile experience later. The result is a meaningfully different product depending on which surface you use.
• Context resets between devices. Logging in on your phone does not mean the AI knows what you discussed on your laptop. Most tools treat each device as a separate session unless you explicitly manage memory settings.
• Actions that work on desktop do not always work on mobile. Integrations, file access, and tool use are often desktop-only or web-only features that have not been extended to the mobile client.
• Notification and proactivity gaps. An AI that can send you a proactive reminder on desktop but not on mobile is only partially useful. True cross-device behavior means the AI can reach you wherever you are.
• Inconsistent interface quality. The same AI can feel excellent on one surface and frustrating on another when the design investment has not been distributed evenly.
• Setup friction multiplies across devices. If connecting an integration requires a desktop browser, users who primarily work on mobile are locked out of key capabilities.

Who Needs a Cross-Device AI Assistant?

• People who move between devices constantly: Someone who starts a task on their laptop, continues on their phone, and needs the AI to know what they were working on without re-explaining it.
• Remote workers: Someone whose work happens across multiple devices and locations, where an AI that only functions well at a desk is limited in practice.
• People with active schedules: Someone who needs their AI to reach them with reminders, updates, and flagged items regardless of which device is in their hand at the moment.
• Knowledge workers in multiple tools: Someone who communicates via email, Slack, and calendar and wants an AI that works in all of those contexts, not just the desktop ones.
• Anyone who tried a single-surface AI and found it limiting: Someone who got value from an AI assistant in one context and wants that value to follow them everywhere they work.

What Makes the Best Cross-Device AI Assistant?

• Consistent capability across every surface, not just consistent branding.
• Persistent memory that is genuinely shared across devices, not just stored in an account that each device reads differently.
• Native apps on the surfaces that actually matter: desktop, mobile, and web at minimum.
• Proactive reach: the ability to send you a notification or message on any surface, not just respond when you open the app.
• Actions that work everywhere, not integrations that only function on desktop.
• Low setup friction when moving to a new device.
• A security model that is clear about what the AI can access from each surface.
• Pricing that does not penalize multi-device use.

Our Review Process

Each tool was evaluated on five criteria based on what cross-device AI use actually demands. Rankings reflect independent assessment only. No affiliate links, no sponsored placements.

• Surface coverage and availability (30%)
• Cross-device memory and context continuity (25%)
• AI quality per surface (20%)
• Setup friction and consistency (15%)
• Pricing value (10%)

Best AI Assistants That Work Across All Your Devices (2026)

1. Vellum

Score: 100/100

Vellum is a personal AI assistant available as a native desktop app, iOS app, and web app, plus Slack and Telegram integrations, with the same persistent memory and context shared across every surface. It is not a web app that was adapted for mobile. Every surface runs off the same AI, the same memory, and the same identity. Vellum has its own email address, takes real-world actions on your behalf, and checks in proactively regardless of which device you are on.

Standout Strengths:

• Available as a native desktop app, iOS app, and web app, plus Slack and Telegram integrations, all sharing the same persistent memory and context across every surface.
• Persistent memory means what you discuss on desktop is immediately available when you check in from your phone, with no need to catch the AI up or re-explain context.
• Its own identity and accounts, including its own email address, so it can take real-world actions on your behalf from any surface, not just respond to you.
• Proactive across every surface: checks in with itself hourly and reaches out with reminders and flagged items regardless of which device you are on.
• Open-source codebase with self-hosting available for users who want full control over their infrastructure and data.
• Fail-closed security: every sensitive action requires explicit permission before it executes, from any surface, every time.

Trade-offs:

• Requires a brief initial setup to connect your email, calendar, and Slack accounts. Most users are up and running in a few minutes.
• Full persistent memory and cross-device sync require a Vellum Cloud account. The free download is available to get started.

Pricing: Free download. Cloud hosting available.

Compared to Others: The tools on this list all share a login across devices. Vellum shares a memory. The difference is that ChatGPT and Claude have memory features that persist facts across sessions, but they do not have the same proactive, action-taking presence across every surface that Vellum does. Vellum does not wait to be opened. It reaches out. It acts. It has its own accounts. No other tool on this list operates that way.

2. ChatGPT

Score: 91/100

ChatGPT is OpenAI's AI assistant, available on web, iOS, Android, Mac desktop, Windows desktop, and Apple Watch. The default model as of 2026 is GPT-5.5 Instant, with Pro users accessing extended context and higher-capability variants. Memory is available and syncs across devices, allowing the AI to retain facts about the user across separate conversations. Free, Plus ($20/month), and Pro ($200/month) tiers are available.

Standout Strengths:

• Available on more surfaces than almost any other tool: web, iOS, Android, Mac, Windows, and Apple Watch.
• Memory that syncs across devices, retaining facts and context across separate sessions.
• Consistent, high-quality AI capability on every surface with no meaningful degradation on mobile.
• Voice mode available on mobile and desktop.

Trade-offs:

• Memory is opt-in and manual. The AI does not proactively build context about you; you manage what it remembers.
• No real-world action capability. ChatGPT responds and generates, but does not take actions on your behalf like sending emails, managing a calendar, or operating in other tools.

Pricing: Free tier available; Plus $20/month; Pro $200/month.

Compared to Others: ChatGPT has the broadest device coverage on this list and a consistent experience across all of them. The gap is memory depth and action capability. It knows what you tell it to remember, but it does not build a working model of you over time the way Vellum does, and it cannot take actions outside the chat window.

3. Claude

Score: 86/100

Claude is Anthropic's AI assistant, available on web, iOS, Android, and Mac desktop. It is well regarded for reasoning, writing, and extended analysis, and has introduced Projects, which give users persistent context organized around specific topics or work areas. Projects sync across devices, so context built on web is available on mobile. Free, Pro ($20/month), and Max ($100 or $200/month) tiers are available.

Standout Strengths:

• Projects provide organized, persistent context that syncs across web and mobile.
• Strong reasoning and writing capability that is consistent across surfaces.
• Mac desktop client with native performance.
• Extended context window on Pro and Max plans for long-form work.

Trade-offs:

• No Windows desktop client. Users on Windows are limited to the web app.
• No real-world action capability. Claude is a conversational and reasoning tool, not an action-taking assistant.

Pricing: Free tier available; Pro $20/month; Max $100 or $200/month.

Compared to Others: Claude is among the strongest AI assistants for reasoning and writing quality, and Projects make it more useful across devices than a standard memory feature. The lack of a Windows client is a real gap, and like ChatGPT, it does not take actions outside the conversation.

4. Perplexity

Score: 81/100

Perplexity is a search-first AI assistant available on web, iOS, Android, and Mac. It builds responses using live web search, providing sourced answers rather than relying solely on training data. The experience is consistent across its web and mobile apps, with search history and saved threads accessible across surfaces. Free and Pro ($20/month) tiers are available.

Standout Strengths:

• Live web search built into every response, with cited sources rather than unverifiable claims.
• Consistent experience across web, iOS, Android, and Mac.
• Search history and thread access across all surfaces.
• Space feature for organizing research and projects across devices.

Trade-offs:

• Primarily a search and research tool. Not designed for taking real-world actions, managing tasks, or operating in other applications.
• No persistent memory about the user in the way that ChatGPT or Vellum offer. Context stays within sessions and organized spaces.

Pricing: Free tier available; Pro $20/month.

Compared to Others: Perplexity is the best tool on this list specifically for research and sourced answers across devices. It has a consistent cross-device experience and is a reasonable everyday AI for people who primarily need factual, cited responses. It is not an action-taking or memory-building assistant.

5. Google Gemini

Score: 76/100

Google Gemini is Google's AI assistant available on web, iOS, and Android. It integrates with Gmail, Google Calendar, Google Drive, and other Workspace tools, allowing it to pull context from your Google account across surfaces. Google One AI Premium ($20/month) provides access to the most capable Gemini model and Workspace integration.

Standout Strengths:

• Deep Google Workspace integration that surfaces relevant context from Gmail, Calendar, and Drive.
• Available on web, iOS, and Android with a consistent experience.
• Gemini Live for real-time voice conversation on mobile.
• Natural access to Google's AI models for users already in the Google ecosystem.

Trade-offs:

• No standalone desktop app. Mac and Windows users access it through a browser.
• Cross-device context is primarily powered by your Google account data. Users outside the Google ecosystem get limited value from the integrations.

Pricing: Free tier available (standard model); Google One AI Premium $20/month for full Gemini model and Workspace integration.

Compared to Others: Google Gemini is the natural choice for heavy Google Workspace users who want AI that understands their Gmail and Calendar on both mobile and web. Outside the Google ecosystem, its cross-device value is more limited, and it does not offer the action-taking capability that Vellum provides.

6. Microsoft Copilot

Score: 71/100

Microsoft Copilot is Microsoft's AI assistant available on Windows (built-in), iOS, Android, web, and Edge. It integrates with Microsoft 365 apps when paired with a Copilot for M365 subscription, but the standalone Copilot app and web experience are available for free. Copilot Pro ($20/month) provides enhanced performance and Microsoft 365 integration.

Standout Strengths:

• Available on Windows, iOS, Android, web, and Edge, covering most surfaces most users work from.
• Built into Windows as a system-level feature, making it accessible without a separate app install on PC.
• Microsoft 365 integration available for Outlook, Teams, and other apps with the right subscription.
• Consistent interface across platforms with shared history.

Trade-offs:

• The Windows experience is strongest. The mobile and web versions are capable but less deeply integrated.
• Microsoft 365 integration requires a separate Copilot for M365 add-on at $30/user/month on top of existing subscription costs.

Pricing: Free tier available; Copilot Pro $20/month; Copilot for M365 $30/user/month add-on.

Compared to Others: Microsoft Copilot has solid device coverage and the strongest Windows integration on this list. For users whose primary device is a Windows PC and whose workflow runs through Microsoft 365, it is the most embedded option. Outside that ecosystem, it is a capable but unremarkable cross-device AI assistant.

7. Notion AI

Score: 66/100

Notion AI is the AI layer built into Notion, available on web, Mac, Windows, iOS, and Android. It assists with writing, summarization, action item extraction, and Q&A across your Notion workspace. Because it is embedded in Notion itself, context from your pages and databases is available to the AI on every surface where Notion runs.

Standout Strengths:

• Embedded in Notion, which already has well-developed native apps on every major surface.
• Context comes from your actual Notion content, giving it grounding in your real notes and documents.
• Consistent experience across Mac, Windows, iOS, and Android.
• Useful for summarizing, drafting, and extracting action items within documents.

Trade-offs:

• Useful only within Notion. It does not function as a standalone AI assistant outside of the Notion context.
• $10/member/month add-on. Users who do not already rely on Notion will not find it worth adopting for the AI alone.

Pricing: Notion AI add-on $10/member/month.

Compared to Others: Notion AI has good cross-device coverage precisely because Notion's own apps are well-built across platforms. But it is a productivity tool add-on, not a personal AI assistant. It cannot take actions outside Notion, does not have persistent memory about you as a person, and does not proactively reach out to you.

8. Mem.ai

Score: 61/100

Mem.ai is an AI note-taking and knowledge management tool available on web, iOS, and Mac. It uses AI to automatically organize notes, surface relevant information across your knowledge base, and assist with writing and summarization. Notes and context sync across web and mobile, giving the AI access to your full note history on any surface.

Standout Strengths:

• AI that surfaces relevant notes and context from your own knowledge base automatically.
• Sync across web, iOS, and Mac keeps your full note history available on any surface.
• Useful for people who capture a lot of information and want AI to make it retrievable.
• Writing and summarization assistance built into the note-taking flow.

Trade-offs:

• Limited to the Mem.ai ecosystem. It does not operate in email, calendar, Slack, or other tools.
• No Windows desktop client. Windows users are limited to the web app.

Pricing: Pricing not listed publicly. Check mem.ai for current plans.

Compared to Others: Mem.ai is the best tool on this list specifically for AI-assisted personal knowledge management across devices. It covers its target use case well. It is not a general-purpose AI assistant and has no action-taking capability outside its own platform.

9. Limitless

Score: 56/100

Limitless is an AI assistant built around passive capture, available on Mac and iOS, with an optional wearable pendant for continuous audio capture across any environment. It records, transcribes, and summarizes conversations throughout the day and makes that content searchable and queryable. Limitless was acquired by Meta in late 2025 and is currently in a transition period.

Standout Strengths:

• Passive capture across Mac and iOS with the pendant extending coverage to any physical context.
• Full-day transcription and summarization that builds a searchable record of your conversations.
• AI that can answer questions about your own day, meetings, and conversations across devices.
• Unique form factor that captures context outside the screen.

Trade-offs:

• Limited to Mac and iOS. No Windows, Android, or web client.
• The Meta acquisition raises open questions about product direction, data practices, and long-term availability.

Pricing: Pricing not listed publicly. Check limitless.ai for current plans.

Compared to Others: Limitless occupies a genuinely different niche than everything else on this list. The passive capture model is a real differentiator, particularly with the pendant. The platform limitations and the uncertainty created by the Meta acquisition are the primary reasons it sits lower on this ranking.

10. Apple Intelligence

Score: 51/100

Apple Intelligence is Apple's AI system available on iPhone 15 Pro and later, iPad with M1 chip or later, and Mac with M1 chip or later. It is built into iOS, iPadOS, and macOS, providing AI assistance in Writing Tools, Mail, Messages, Photos, Safari, and other system apps. Apple Intelligence runs primarily on-device, with some capabilities routed through Private Cloud Compute for more demanding requests. It is free for compatible Apple hardware at no additional subscription cost.

Standout Strengths:

• Built into the operating system across iPhone, iPad, and Mac, requiring no separate app or account.
• On-device processing for many features, with a documented Private Cloud Compute architecture for requests that require server processing.
• Free for compatible Apple hardware with no subscription.
• Deep integration with native Apple apps: Mail, Calendar, Messages, Notes, Photos.

Trade-offs:

• Apple ecosystem only. Not available on Android or Windows.
• Requires recent Apple hardware (iPhone 15 Pro or later, M1 chip or later on iPad and Mac). Older devices are not supported.

Pricing: Free for compatible Apple devices. No additional subscription required.

Compared to Others: Apple Intelligence is the only tool on this list that is genuinely embedded at the operating system level, which gives it access to your apps and content in a way that no third-party assistant can match on Apple hardware. The limitation is the ecosystem wall: it only works on Apple devices, and it does not proactively reach out, take actions beyond native apps, or build a working model of you over time.

Cross-Device AI Assistant Comparison Table

Why Vellum Stands Out

ChatGPT covers the most surfaces. Apple Intelligence is the most deeply embedded on Apple hardware. Claude has the strongest reasoning quality per session. These are real strengths that earned their rankings.

What none of them do is operate as a persistent, proactive presence across every surface at once. They respond when you open them. They do not reach out. They do not act. They do not have their own email address or their own accounts. When you close the app, the AI waits.

Vellum was built around a different idea: the AI should be available when you open it and active when you do not. It checks in with itself every hour, reviews its context, and reaches out across whatever surface makes sense, whether that is a desktop notification, a Slack message, or an iOS push. It does not require you to come to it.

The memory architecture is what makes this work in practice. ChatGPT and Claude both have memory features that save facts across sessions. Vellum's memory is not a list of facts you told it to save. It is a persistent context that builds up over time across every conversation on every surface, and the AI uses that context actively, not just when you ask it to recall something.

The action capability is the other major difference. Vellum can send emails from its own address, manage your calendar, post to Slack, make phone calls, update Linear tickets, and more, from any surface it runs on. No other tool on this list takes real-world actions on your behalf across that range of integrations.

A few specific comparisons worth highlighting:

Vellum vs ChatGPT: ChatGPT has more surfaces (including Android, which Vellum does not yet have) and the most consistent general-purpose AI quality across all of them. Vellum has persistent working memory, proactive reach, and real-world actions that ChatGPT does not offer.

Vellum vs Apple Intelligence: Apple Intelligence is unmatched for on-device privacy and OS-level integration on Apple hardware. Vellum works across Apple hardware, non-Apple devices, and communication tools like Slack and Telegram in a way that Apple Intelligence cannot.

Vellum vs Claude: Claude's Projects give it good cross-device context for organized work. Vellum's context is not organized into Projects; it accumulates naturally across everything you do, and the AI applies it without you having to manage it.

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FAQs

What makes an AI assistant truly cross-device?

A truly cross-device AI assistant maintains consistent capability and shared memory across every surface where you use it. That means the same context, the same quality of responses, and the same ability to take actions whether you are on your laptop, phone, or browser. Logging in on multiple devices is the baseline. Shared persistent memory and consistent behavior across all of them is the real bar.

Which AI assistant has the best memory across devices?

Vellum has the most developed cross-device memory on this list. Its persistent memory is shared across the desktop app, iOS app, web app, Slack, and Telegram, and the AI uses it actively rather than waiting for you to reference it. ChatGPT and Claude both have memory features, but they are opt-in and session-managed rather than continuously building context from everything you do.

Does Vellum work on Android?

Vellum currently offers a native desktop app, iOS app, and web app, plus Slack and Telegram integrations. Android users can access Vellum through the web app or via Slack and Telegram. Native Android app availability is something to check at vellum.ai for current status.

Is ChatGPT available on all devices?

Yes. ChatGPT is available on web, iOS, Android, Mac desktop, Windows desktop, and Apple Watch, making it the most broadly available AI assistant on this list. Memory syncs across devices with the memory feature enabled.

What is Apple Intelligence and which devices support it?

Apple Intelligence is Apple's AI system built into iOS, iPadOS, and macOS. It is available on iPhone 15 Pro and later, iPad with M1 chip or later, and Mac with M1 chip or later. It is free for compatible hardware with no additional subscription. Apple Intelligence runs primarily on-device, with some features handled through Apple's Private Cloud Compute infrastructure.

Is there a free AI assistant that works across devices?

Yes. Vellum is free to download and works across desktop, iOS, web, Slack, and Telegram. ChatGPT, Claude, Perplexity, Google Gemini, and Microsoft Copilot all have free tiers with cross-device access. Apple Intelligence is free for compatible Apple hardware.

How does Vellum compare to ChatGPT across devices?

ChatGPT covers more raw surfaces, including Android and Apple Watch, and has a consistent high-quality experience on all of them. Vellum covers desktop, iOS, web, Slack, and Telegram with shared persistent memory that builds over time, plus the ability to take real-world actions on your behalf. The right choice depends on whether you need the broadest possible surface coverage or a deeper AI that actively works for you.

Can an AI assistant be proactive across devices?

Yes, and this is one of Vellum's primary differentiators. Vellum checks in with itself every hour and sends notifications or messages across whatever surface is relevant when something needs your attention. Most other AI assistants on this list are reactive: they respond when you open them but do not reach out on their own.

Which AI assistant works best for people who use both Apple and non-Apple devices?

Vellum is the strongest option for users across mixed device environments because it is not tied to any one operating system or hardware ecosystem. It runs on desktop, iOS, web, Slack, and Telegram regardless of the underlying device. ChatGPT also has solid cross-ecosystem coverage on web, iOS, Android, Mac, and Windows.

Is Limitless still available after the Meta acquisition?

Limitless was acquired by Meta in late 2025 and is currently in a transition period. The product is still available as of this writing, but the long-term roadmap and data practices under Meta ownership are not yet fully documented. Users who rely on Limitless for passive capture should monitor for changes in availability and terms.

How does Vellum handle security across multiple devices?

Vellum uses a fail-closed permissions model across every surface it runs on. Every sensitive action, whether triggered from desktop, iOS, web, or Slack, requires explicit approval before it executes. Your workspace, memory, and configuration are stored in a private, encrypted Vellum Cloud account that you control, with export available at any time. The security model does not vary by device.

Extra Resources

• Best Personal AI Assistants in 2026: Reviewed and Compared →
• Your AI Assistant Should Work for You, Not Worry You →
• 10 Best OpenClaw Alternatives in 2026: Reviewed & Compared →
• Is Claude Better Than Gemini? Here's the Honest Answer →

Citations

[1] Grand View Research. (2025). Conversational AI Market Size, Share & Trends Analysis Report. Grand View Research.

[2] Apple. (2024). Apple Intelligence Is Available Today on iPhone, iPad, and Mac. Apple Newsroom.

[3] McKinsey & Company. (2025). Superagency in the Workplace: Empowering People to Unlock AI's Full Potential. McKinsey Global Institute.

[4] Microsoft. (2024). 2024 Work Trend Index Annual Report: AI at Work Is Here. Now Comes the Hard Part. Microsoft WorkLab.