The problem
Every developer has the same ritual: open a dozen browser tabs to handle simple tasks. One site to decode a JWT. Another to test CORS headers. A third for regex. A fourth that is buried under ads and wants you to sign up before it shows you anything useful.
Most of these tools solve one specific problem and do it reasonably well. But having 10 bookmarks for 10 single-purpose sites is exhausting, and many of them ship your data to a server you know nothing about.
What LanternKit is
LanternKit is a suite of free developer tools under one domain. No sign-up. No ads. No tracking cookies. Most tools run entirely in your browser — your data never leaves your device.
The tools cover the tasks developers reach for most often: inspecting HTTP requests, transforming data formats, generating IDs, decoding tokens, testing regex patterns, and previewing how content looks before it ships.
Tools available today
HTTP & Web
- CORS Tester — send a preflight or simple request and inspect the actual response headers
- API Request Builder — build and fire HTTP requests with custom headers and body
- Redirect Checker — follow HTTP redirect chains hop by hop
- HTTP Header Analyzer — fetch and explain response headers
- Robots.txt & Sitemap Validator — check your robots.txt and sitemap for errors
Data & Formats
- Data Format Converter — convert between JSON, YAML, TOML, CSV, XML, and SQL
- Diff Viewer — side-by-side text diff with highlighted changes
- Markdown to HTML — live preview with sanitized output
- JSON Schema Generator — generate a draft-07 schema from sample JSON
- SVG to PNG — export SVG markup as a PNG at any resolution
Security & Auth
- JWT Decoder — decode header and payload, highlight expiry claims
- Regex Tester — test JavaScript regex with live match highlighting
- SSL Certificate Monitor — check TLS certificate validity, expiry, and issuer details
Generators
- ID Generator — UUID v4/v7, ULID, Nano ID, and CUID2
- Cron Expression Builder — visual builder with human-readable explanation and next-run times
- UTM Builder — build and parse UTM-tagged URLs
- AI for Marketing — generate launch copy for Product Hunt, Twitter, LinkedIn, and Reddit — useful when shipping something new
SEO & Meta
- OG Preview — preview how a URL looks when shared on social platforms
Edge-native by default
LanternKit runs on Cloudflare Workers with server-side rendering. Pages load fast globally. Tools that require a server (CORS testing, redirect following, OG preview fetching) proxy through the Worker; everything else runs client-side in your browser.
What's next: Pro features
The free tools stay free. I'm building a Pro tier focused on persistence and monitoring — the things a free, client-side tool cannot do:
- Webhook Inbox — a limited free tier is live now; Pro adds persistence, 90-day retention, and replay
- Cron Job Monitor — heartbeat monitoring for your scheduled jobs, with email and Slack alerts
- Mock API Sandbox — define mock endpoints and test against them without a real backend
- Saved history and presets — search past runs, save cron schedules, regex snippets, and UTM templates
Each of these workflows typically requires a separate paid subscription to a dedicated service. LanternKit Pro is currently planned at EUR 12/month.
Try it
Pick any tool from the homepage and try it. No sign-up, no install, no waiting. If something's broken or missing, use the feedback button at the bottom of any page.