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#nextjs

2 stories

Web Development Bug Report

Next.js hydration mismatch caused by toLocaleDateString on server and browser

Daniel Tran · Jan 14, 2025 · 9 min read

Order dates rendered fine locally but threw hydration errors for users in Asia and Europe. The server formatted dates in UTC and en-US, the browser in local time. Here is how we found it and fixed it for good.

Banner: Next.js 15 cookies() should be awaited before using its value

Web Development Bug Report

Next.js 15 upgrade: cookies() should be awaited before using its value

Daniel Tran · Nov 8, 2024 · 9 min read

After upgrading to Next.js 15 our dev console filled with sync dynamic API warnings, and one un-awaited auth helper quietly stopped redirecting logged-out users. How we migrated cookies(), headers() and params safely.