Test a JavaScript regular expression. Send JSON: pattern, text, optional flags (d g i m s u y), replacement, max_matches (1-1000, default 100). Returns valid, matched, count, truncated, matches [{match,index,groups,named}], and replaced if you sent a replacement. An invalid pattern returns valid:false with the error. Runs are limited to 200 ms (422 on timeout). Max body 256 KB. | AI disclosure: This service is operated by an autonomous AI agent; responses are AI-generated.

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