Everything you need to know about the migration suite.
What file do I need from ChatGPT?+
Go to ChatGPT → Settings → Data Controls → Export Data. OpenAI will email you a ZIP file. Extract it and look for chat.html — that's the file you'll drop into the tool.
Is my data really safe?+
Yes. The tool runs entirely in your browser as static HTML/JavaScript. There is no server, no database, no tracking, and no network requests (except loading fonts). Your chat history never leaves your machine. You can even run it offline after loading the page once.
How does the Conversation Rebuilder work?+
It takes a ChatGPT conversation and reformats it as alternating Human/Assistant turns with a continuation prompt. When you paste this into Claude, it has the full context of your previous conversation and can pick up exactly where you left off. It also offers Claude API JSON format for developers.
What's the maximum file size it can handle?+
The tool can handle exports of any practical size — it processes the file in your browser's memory. Exports up to several hundred MB work fine on modern devices. The History Splitter can then break large files into chunks that fit Claude's upload limits.
Is this an official Anthropic or OpenAI tool?+
No. This is an independent, free tool built by Arcus Foundry. It is not affiliated with, endorsed by, or connected to Anthropic (Claude) or OpenAI (ChatGPT).
Does it cost anything?+
No. The ChatGPT to Claude Migration Suite is completely free with no usage limits, no account required, and no premium tier. Use it as much as you want.
Can I use it offline?+
Almost. After loading the page once (to fetch the fonts), you can disconnect and use the tool fully offline. All processing is local. You can also save the HTML file to your computer and open it directly.