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Feature checklists make every tool look equivalent. This table leads with the three things that actually differ — what it costs you before it works, whether your files leave your device, and where the free version stops.
| NotebookLMnotebooklm.google.com | Perplexityperplexity.ai | ChatGPTchatgpt.com | DeepSeekdeepseek.com | |
|---|---|---|---|---|
| What it does | Summarises only the sources you upload, and cites the exact passage | Answers a question by searching the web and footnoting every claim | The general assistant most people mean when they say they used AI | Open-weight reasoning model you can use free in a chat window |
| What it costs you | Free accountFree to use, but you have to register before it will do the job. | Free tierA genuinely usable free tier with paid plans for volume or team features. | Free tierA genuinely usable free tier with paid plans for volume or team features. | Free accountFree to use, but you have to register before it will do the job. |
| Your files | Runs on their server | Runs on their server | Runs on their server | Runs on their server |
| Where it stops | Needs a Google account, and each notebook takes a fixed number of sources with a word cap per source. | The deeper Pro search mode is limited to a few runs a day without a subscription. | Free accounts are rate-limited on the best model and get downgraded to a smaller one mid-session without warning. | Needs an account to send a single message, and capacity has been unavailable at peak times more than once. |
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| Category | AI Assistants & Generators | AI Assistants & Generators | AI Assistants & Generators | AI Assistants & Generators |
| Last checked | 2026-07-29 | 2026-07-29 | 2026-07-29 | 2026-07-29 |
| Open the site | Open | Open | Open | Open |
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