Interactive playgrounds for developer libraries

Parse CSV, inspect delimiter, headers, rows and formula injection without sending files outside the browser.

Compare Testing Library query families and variants against a sanitized DOM snapshot without uploading HTML.

Query JSON, inspect values, paths and JSON Pointers, and keep filters in safe mode without uploading payloads.

Explain cron expressions, preview next runs and review timezone/DST caveats without scheduling jobs.

Parse .env snippets, inspect duplicate keys and keep secret-like values masked by default.

Preview Autoprefixer output, grid caveats and prefix cleanup without sending CSS outside the browser.

Check target browsers, coverage caveats and Browserslist query diagnostics without sending data outside the browser.

Evaluate npm semver ranges against candidate versions with normalized comparators, prerelease behavior and a private browser worker.

Convert JSON Schema into TypeScript declarations with local refs, unions, enums and safety diagnostics in a private browser worker.

Simulate Axios request config, validateStatus behavior, interceptor order, timeout outcomes and secret masking without sending network traffic.

Inspect Vite config snippets without running project code and review server, build, alias, env, plugin and Vite 8 diagnostics.

Transform JavaScript, JSX and TypeScript snippets with Babel in a private browser worker and inspect code, diff and pipeline notes.

Validate JSON payloads with a controlled Joi schema DSL in a browser worker without executing raw JavaScript.

Transform TypeScript, JSX and JavaScript snippets with esbuild-wasm in a browser worker without uploading code.

Generate deterministic sample JSON from a JSON Schema for docs, mocks and tests without sending schemas to a backend.

Visualize RxJS-style marble timelines for map, filter, take, debounceTime, mergeMap and switchMap in deterministic virtual time.

Practice Playwright-style locators, accessible names, strictness diagnostics, filter hasText and nth against a sanitized DOM snapshot.

Test date-fns format tokens, parseISO, custom parse, locale options, protected token warnings and formatDistance in the browser.

Compare Jest-style matcher behavior, PASS/FAIL output, .not, expected versus received diffs and JSON-only edge cases in the browser.

Validate YAML syntax, convert YAML to JSON and inspect diagnostics, multi-document streams and tree paths in the browser.