Changelog

A tool that never changes is a tool nobody maintains. This page is dated so you can tell the difference. Entries come from this repository's commit history for the regexcalc app and the shared code it builds with — not from the build clock, and not from work that shipped on sibling domains.

2026-10-08

• Ad tiers are now chosen by rendered fill, not by whether the ad tag loaded. Tag presence and a rendered creative are different facts. Choosing a layout before a creative with real dimensions exists is how a page grows a permanent grey box, and it meant the reported tier had no relationship to what visitors saw.
• Sitemaps generated from build output, with only registered domains listed. Hand-maintained sitemaps drift the moment a page is renamed, and a stale lastmod on a dead page teaches crawlers to ignore the field everywhere else.

2026-10-06

• Colour-contrast fixes to meet WCAG 2.1 AA. Muted text on the dark theme and the accent used for the status pill both missed 4.5:1. That pill is what tells you "Pattern Valid" versus "Syntax Error", so poor contrast there was an accessibility bug and a correctness bug.

2026-10-03

• Four guides added in one content batch, each written from patterns tested on this runtime rather than from a scraped list.

2026-10-01

• Guides published: cheat sheet, regex hacks, ReDoS protection. The ReDoS page exists because this tester is where people discover exponential backtracking, and finding it there with no explanation of why it hangs is a dead end.
• Regex replace tool added as its own page with related guides beneath it. Extraction and substitution are different jobs; the main tool only did the first, and bolting a replace preview onto it would have made both worse.
• Related-guides blocks added under guide pages so a page connects to its neighbours instead of sitting alone.
• Build-time 404 and contact pages. A soft 404 — an error page served with status 200 — is a common reason a small site fails an ad-network review, and it is entirely avoidable. The contact page gave defect reports somewhere to land.

2026-09-16

• Sitemap lastmod values refreshed, lockfile updated. No behavioural change to the tester that day — worth stating plainly, because an entry implying a fix where there was none is worse than no entry.

2026-09-15

• Publisher records (ads.txt / app-ads.txt) added and growth tooling wired up. Publisher records let ad systems verify who may sell this inventory; without one, demand sources that check bid less or not at all.

First release

• Client-side tester: live recompile on every keystroke via new RegExp, flag toggles for g, i, m, s, match list with indices, positional capture-group output, and five recipes (email, URL, IPv4, semver, UUID) that load their own sample text. The engine is your browser's — see what this runtime accepts before assuming portability.

Something broken, or a pattern you believe this tool mishandles? Tell me — a reproduction with the exact pattern, flags, and input is the most useful mail this site gets.