Simon Willison’s Weblog

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23rd December 2025

Research url-limits-investigation — Major browser engines demonstrate significant differences in how they enforce URL length limits. Chromium sets a 2 MB cap at its inter-process communication boundary, rejecting longer URLs when crossing processes. Firefox relies on user-configurable preferences, employing a 1 MB "standard" limit but permitting up to 512 MB in absolute terms, with stricter limits (2,000 characters) for history and bookmarks.

This is a beat by Simon Willison, posted on 23rd December 2025.

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