Why Nobody Can Agree on Claude's Custom Instructions Character Limit

One provider publishes a number, one doesn't as clearly

Search for ChatGPT's custom instructions character limit and you'll get a consistent, officially documented answer: 1,500 characters per field on Free and Go plans, expanded to 5,000 characters on Plus, Pro, Team and Enterprise plans following a 2026 update. Search for the equivalent limit on Claude's profile preferences or Claude Projects custom instructions, and you'll find numbers that are widely repeated (around 1,500 characters for profile-level instructions, around 8,000 for Projects) but far less consistently sourced back to an official, prominently published statement.

Why this gap exists

Different companies document product limits with different levels of formality and prominence. A limit can be real and enforced in the product without being written down anywhere as clearly as a help-center article with a specific number — which means the "commonly cited" figure users pass around is often based on testing and shared experience rather than an official spec sheet.

What this means for you practically

It doesn't mean the commonly cited numbers are wrong — they're usually close, based on real user testing. It means you shouldn't treat an unofficial number with the same confidence as an officially documented one, and you should expect it might shift without an announcement, since there's no public commitment being changed when it does.

A checker that admits what it doesn't know

Our Custom Instructions Character Limit Checker includes presets for both officially documented and commonly reported limits, but every limit field stays editable — so if you discover through actual testing that a limit has shifted, you're never stuck trusting a number this page can't independently verify for you.