Why a plain find-and-replace corrupts a WordPress dump
WordPress stores arrays and objects — widget settings, theme mods, page-builder layouts, plugin options — as PHP serialize() strings, and each string records its length in bytes: s:19:"http://old.test/x". A text editor's find-and-replace changes the URL but not the 19, so PHP can no longer unserialize the value and the setting silently breaks after import. Changing a domain is the classic trigger, because the new host is almost never the same length as the old one.
How this tool works
Upload the dump and the tool scans it for single-quoted SQL string literals (the actual column values), unescapes each one, and tries to unserialize it. If the value is serialized, it replaces inside every string and re-serializes with freshly counted lengths; if it isn't serialized, it does a normal replace. Everything is re-escaped and reassembled into a downloadable .sql that is a drop-in replacement for your dump. It processes the whole file in one pass when you click — nothing is sent anywhere.
Using it
Plain text
Leave the boxes unchecked for a literal swap — e.g. find http://old.test, replace with https://new.example. Tick Case-insensitive to ignore letter case.
Regular expression
Tick Regular expression to use a JavaScript regex in Find (applied globally); use $1, $2 in Replace with for capture groups. Useful for protocol-relative or wildcard host changes.
Limits & alternatives
It handles standard mysqldump / phpMyAdmin exports (backslash and doubled-quote escaping). Serialized PHP objects (O:) are left untouched and replaced as plain text, so review those. Very large dumps are processed in memory, so extremely big files are bounded by your browser's available RAM. For a live database, WordPress's own WP-CLI search-replace is the safest route; to fix a single value by hand use Serialized Search-Replace, and to repair already-broken lengths use Fix Serialized Data.
Privacy
Your dump is parsed entirely in your browser — it is never uploaded. That matters: a database export is exactly the kind of file you don't want to hand to a web service.