Most days at a terminal, I lose ten minutes to one of two stupid problems:
- Writing a regex I half-remember the syntax for.
- Pasting a payload into a parser and watching it reject me because somebody, somewhere, left a trailing comma.
I shipped two free tools that close both holes. Both run in the browser, both use Claude under the hood for the AI fallback, both have zero login.
regexai — describe it, get the regex
- Live: regexai-six.vercel.app
- Type
match phone numbers in (xxx) xxx-xxxx format, hit Build. Get a regex, the flags, a generated test string, and a plain-English explanation of every group. - Bonus: live test mode highlights matches as you tweak the pattern.
jsonfix — paste broken JSON, get clean JSON
- Live: jsonfix-lake.vercel.app
- Format, minify, or AI-fix. The fix tab takes input that's missing quotes, has trailing commas, or has the wrong nesting, and rewrites it correctly — with an explanation of what was broken.
The pattern
- Deterministic path first. regexai runs your regex through native
RegExpand highlights matches as you type. jsonfix callsJSON.parseand formats. No API, no latency, no cost. 95% of sessions never leave this path. - AI fallback. If the deterministic path fails, one button hands the problem to Claude (haiku-4-5) with a tight prompt and a JSON schema. Result lands back in the same UI.
- No login, no quota, no upsell. Friction kills these utilities. The cost per session is low enough that I eat it.
Why this shape wins
Chat re-establishes context every turn. A textarea doesn't. For chores you do more than once a week, the page wins on activation energy alone. ChatGPT is great for novel problems. It's wrong for the 30th time this month you needed to validate an IPv4.
Stack
- Next.js 16 App Router
@anthropic-ai/sdk, modelclaude-haiku-4-5- Edge runtime
- Vercel analytics, no DB, no auth
What's next in this shape
- cron expression builder
- SQL → English explainer
- curl → fetch/requests converter
- diff → plain English summary
Try them
Both free, both no-login. Bookmark the one you'll actually use.
Open regexai → Open jsonfix →Want this pattern applied to building MCP servers? The MCP Boilerplate ($79) is the same idea: deterministic scaffold, AI in the fallback.