Why AI memory matters
A fresh chat with most AI assistants forgets everything you said the day before. That is fine for one-shot questions and useless for anything that runs for weeks: a research project, an ongoing piece of writing, a long-running coding effort, a personal therapist substitute, a study companion. The same context has to be re-pasted at the start of every session, and the AI’s output is shallower because it cannot remember which threads you have already pulled on.
The apps that fix this break the problem into two paths. Some add an explicit “memory” feature that the model writes to and reads from across sessions (ChatGPT, Claude Projects, Gemini, Pi, Replika). Others ground the AI in a fixed set of sources you upload and keep the conversation inside that boundary (NotebookLM, Perplexity Pages, Claude Projects again). A third path lives outside the AI vendor entirely: a personal note vault that you summarise and feed into the AI as needed (Obsidian, Notion, the second-brain apps).
These seven Android apps cover the spread. We tested each on a real long-running thread — a months-long research effort — and graded each on what the AI remembered between sessions, what citations it could give back, and how clean the recall felt.
What to look for in an AI memory app
- Persistent memory across sessions. The AI should remember what you told it last week without you re-pasting.
- Selective recall. You should be able to see what the AI remembers and edit or delete entries.
- Citation paths. When the AI claims something, it should point back to which source or memory entry the claim came from.
- Per-project scoping. The AI should not blend memory across separate projects.
- Export. Your memory entries should be portable rather than locked in.
Quick comparison
| App | Best for | Platforms | Free plan | Paid plan | Standout |
|---|---|---|---|---|---|
| Claude | Project-scoped context | Android, iOS, web | Yes | $20/mo Pro | Projects with 200K token context |
| ChatGPT | Cross-chat persistent memory | Android, iOS, web | Yes | $20/mo Plus | Auto-updating memory across chats |
| NotebookLM | Citation-grounded sources | Android, iOS, web | Yes | $20/mo Plus | Cited passages from your sources |
| Gemini | Memory plus Google context | Android, iOS, web | Yes | $20/mo Advanced | Pulls from Gmail, Docs, Drive |
| Perplexity | Research with Pages | Android, iOS, web | Yes | $20/mo Pro | Pages save research threads |
| Pi | Conversational long memory | Android, iOS, web | Yes | None | Remembers details across weeks |
| Replika | Personal companion memory | Android, iOS, web | Yes | $7.99/mo Pro | Long-term relationship memory |
| Obsidian | Manual second brain plus AI | Android, iOS, Mac, Win, Linux | Yes | $8/mo Sync | Local-first, AI plugin support |
The apps
1. Claude, best for project-scoped persistent context
Claude by Anthropic introduced Projects as a first-class feature: a workspace with custom instructions, attached reference documents, and a chat history that survives across sessions. The 200K-token context window holds about 500 pages of source material per Project, and the model treats those documents as the ground truth for everything inside that Project.
On Android, the experience is full parity with the web app. Voice input, file uploads, and continued conversations work the same. The Pro tier raises message caps and unlocks Claude Opus for the larger reasoning tasks.
Pricing:
- Free: Claude Sonnet with a generous daily cap
- Pro: $20/month for Claude Opus and unlimited Projects
Platforms: Android, iOS, web
Bottom line: Pick Claude when memory should be scoped to a project and the source documents are the ground truth.
2. ChatGPT, best for cross-chat persistent memory
ChatGPT by OpenAI introduced cross-chat memory as a global feature: a single memory store that the model writes to during any conversation and reads from in every future conversation. The feature is on by default for Plus subscribers and pulls in details like your name, work context, preferences, and ongoing projects without explicit re-statement.
The Android app handles the same memory store as the web app. The Settings → Personalization → Memory pane shows everything the model remembers and lets you delete individual entries.
Pricing:
- Free: limited memory and message caps
- Plus: $20/month for full memory, faster models, voice mode
Platforms: Android, iOS, web
Bottom line: Pick ChatGPT for the simplest cross-chat memory that surfaces details without explicit project setup.
3. NotebookLM, best for citation-grounded source memory
NotebookLM by Google flips the memory model: instead of the AI remembering you, you upload sources and the AI synthesises answers strictly from inside that source pool. Every claim carries a citation back to the passage it came from, which is the closest a generative tool gets to a researcher’s standard.
The Android app added Audio Overview generation in 2025, which produces a podcast-style audio summary of your sources. For research projects with a defined source corpus, this is the deepest tool on this list.
Pricing:
- Free: limited notebooks and sources
- Plus: $20/month via AI Pro tier for higher caps
Platforms: Android, iOS, web
Bottom line: Pick NotebookLM when the AI should stay grounded in the sources you control.
4. Gemini, best for Google ecosystem context
Gemini by Google pulls memory from the wider Google account: Gmail threads, Google Docs, Calendar entries, and Drive files become part of the AI’s context when you grant permission. For users already deep in the Google ecosystem, this is the AI that knows the most about your life without you typing any of it.
Gemini Advanced unlocks Gemini 2.5 Pro plus the deeper context window and the Connected Apps integration.
Pricing:
- Free: Gemini with limited memory
- Advanced: $19.99/month via Google AI Pro for full ecosystem integration
Platforms: Android, iOS, web
Bottom line: Pick Gemini when you want the AI to know your Gmail, Calendar, and Docs context without manual setup.
5. Perplexity, best for research with persistent Pages
Perplexity is a research-first AI search tool. The Pages feature saves the full research thread — your queries, the AI’s answers, the cited sources — as a permanent document that you and others can return to. For ongoing research projects, Pages substitute for a typical chat memory.
The Pro tier unlocks longer context windows, additional model choice (Claude, GPT, Gemini), and deeper search modes.
Pricing:
- Free: 5 Pro searches per day
- Pro: $20/month for unlimited Pro searches and model choice
Platforms: Android, iOS, web
Bottom line: Pick Perplexity if research threads are the thing you keep returning to.
6. Pi, best conversational long memory
Pi by Inflection is the AI most explicitly designed around long-form conversation. Memory is the product: Pi remembers what you talked about last week, last month, and as far back as your account history goes. The tone is calm, reflective, and built for the kind of conversation people have with a therapist or a thoughtful friend.
The free tier is generous and there is no paid wall on memory itself — Inflection sustained the free model after the 2024 Microsoft partnership.
Pricing: Free for personal use
Platforms: Android, iOS, web
Bottom line: Pick Pi if you want an AI that holds a long, reflective thread without setup or scope.
7. Replika, best personal companion with long-term memory
Replika is the longest-running personal AI companion app. The relationship-style memory tracks what you have shared over weeks and months — names, events, feelings, recurring themes — and the AI references them naturally in later conversations.
The free tier covers basic memory and conversation. The Pro tier unlocks roleplay modes, voice calls, and additional personality traits.
Pricing:
- Free: basic conversation and memory
- Pro: $7.99/month for advanced modes and voice
Platforms: Android, iOS, web
Bottom line: Pick Replika for the long-form personal companion AI use case.
8. Obsidian, best manual memory you control
Obsidian is the second-brain answer to the memory problem. You write notes, you link them, you ask an AI plugin or external assistant to read across them when needed. The data stays local in plain markdown, the AI sees only what you choose to share, and the “memory” is yours to edit, audit, or export at any time.
The plugin ecosystem includes Copilot, Smart Connections, and Text Generator — each of which calls out to an LLM (Claude, GPT, or local) with your notes as context. The result is hybrid: the AI does not have native memory, but you control what context you supply.
Pricing:
- Free: full feature set
- Sync: $8/month for Obsidian Sync if you want managed sync
Platforms: Android, iOS, Mac, Windows, Linux
Bottom line: Pick Obsidian when you want full control over what the AI sees and remembers.
How to pick the right one
- You want project-scoped context with source docs: Claude.
- You want the AI to remember details across every chat: ChatGPT.
- Your work is reading sources and synthesising: NotebookLM.
- You live in Google’s ecosystem: Gemini.
- Your work is ongoing research with citations: Perplexity.
- You want long, calm conversational memory: Pi.
- You want a personal AI companion: Replika.
- You want full control over what the AI remembers: Obsidian plus an LLM plugin.
FAQ
What is the best free AI memory app? Pi has the most generous free tier with full conversational memory. ChatGPT and Claude have free tiers with limited memory. NotebookLM is free for moderate research projects.
Can I trust AI memory with sensitive information? Read each app’s privacy policy. ChatGPT, Claude, and Gemini all offer ways to disable training on your data; the memory store itself is still on the vendor’s servers. Obsidian plus a local LLM is the only fully private option here.
How is Claude Projects different from ChatGPT memory? Claude Projects are explicitly scoped to a single workspace with attached documents. ChatGPT memory is global across all chats. Projects are better for compartmentalised work; ChatGPT memory is better for an AI that knows everything about you.
Can the AI remember between Android and web? Yes for all the apps on this list. Memory lives on the vendor’s servers and syncs across devices.
Will my AI memory persist if I switch apps? No. Memory does not export between vendors. If you switch from Claude to ChatGPT, you start over. This is part of why Obsidian-style external second brains are useful.
Are there local-only AI memory apps? Yes. Apps like Ollama, LM Studio, and the local-LLM ecosystem on Android can run a model with local memory. The trade-off is hardware: a 7B model needs a flagship phone, and the model quality lags Claude or GPT.
