· dev tools + references
Dev tools, in one place.
Free browser-only developer utilities: a live regex tester with cheat sheets (including Python), a UUID generator covering v1 through v7, and a bidirectional JSON ↔ CSV converter with Excel-compatible output. No signup. No server round-trip. Nothing uploads.
Tools.
· interactive · browser-only
· tool · 2026-05-01
Email deliverability checker
Paste any domain to check SPF, DMARC, DKIM, and MX in one lookup. Pass/warn/fail badges with plain-English findings and remediation. Probes 25 common DKIM selectors in parallel. DNS-over-HTTPS, runs entirely in browser.
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· tool · 2026-04-21
Regex tester
Live match highlighting, capture groups (numbered + named), replace mode, and six flag toggles (g / i / m / s / u / y). ECMAScript flavor, browser-only, no signup.
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· tool · 2026-04-21
UUID generator
Generate v4 (random), v7 (time-sortable, RFC 9562), v1 (legacy), or nil UUIDs. Bulk up to 1,000. Four format options (standard / braces / no-hyphens / UPPERCASE). Cryptographically secure via Web Crypto.
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· tool · 2026-04-22
Base64 encoder / decoder
Bidirectional text ↔ base64 with UTF-8 awareness (emoji, accents, CJK), standard and URL-safe variants, file upload for binary encoding, and live image preview for decoded PNG/JPG/GIF/WebP.
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· tool · 2026-04-21
JSON ↔ CSV converter
Bidirectional JSON ↔ CSV with nested-object flattening (dot notation), five delimiters, quote styles, Excel BOM, and line-ending selector. File upload, download, copy.
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· tool · 2026-04-21
JSON to Excel
Same JSON ↔ CSV tool, Excel-forced defaults: UTF-8 BOM on, CRLF line endings, always-quoted fields. Download a .csv that Excel opens correctly on the first double-click.
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· tool · 2026-04-21
CSV to JSON
Paste CSV, get a pretty-printed JSON array of objects. Handles quoted fields, escaped quotes, newlines inside cells. Auto-parses numbers and booleans so the output is immediately usable.
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· tool · 2026-04-24
Barcode generator
QR codes plus 9 one-dimensional formats (Code 128, EAN-13, UPC-A, ITF-14, Code 39, MSI, Codabar, Pharmacode, EAN-8). Custom colors, sizes, error correction. Download PNG or SVG. Client-side only.
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References.
· cheat sheets · syntax reference
· reference · 2026-04-21
Regex cheat sheet
Every metacharacter, quantifier, anchor, character class, group type, and look-around, with eight production-grade patterns (email, phone, URL, date, IPv4, hex color, whitespace, trim).
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· reference · 2026-04-21
Python regex cheat sheet
Every method of Python's re module (search / match / fullmatch / findall / finditer / sub / subn / split / compile / escape), every flag, and the syntax differences from JavaScript regex.
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Why these, and why browser-only
Every developer has a pinned tab for a regex tester, a UUID generator, and a format converter. Most of those tabs point at sites that want your email, nudge you toward a signup, or quietly send your data somewhere for analytics. The browser can do all of this work locally. The regex engine is native, UUID generation is in the Web Crypto API, and parsing CSV is about 40 lines of JavaScript, so there's no real reason to upload anything.
The tools here are the ones we use daily. They're deliberately narrow. The regex tester is ECMAScript-flavor only (not PCRE, not Python, not Java) because that's what most devs are writing regex for when they open a browser tab, and because shipping five flavors means maintaining five engines. The UUID generator doesn't try to pretend it can give you a real MAC-based v1. The browser can't see your MAC, so the node portion is random and we say so. The JSON ↔ CSV converter handles nested objects with dot notation because that's what people actually want.
Missing a tool? Email us. The next thing we ship is usually whatever a developer asked for twice in a week.