Internet Library
Tools worth bookmarking
A short, opinionated list of browser tools we actually use. No sign-up walls, nothing that needs an account to try. Broken links get removed rather than replaced. These are all other people's tools — the ones we build are in the Lab.
Text & data
6Transform, validate and convert data between formats.
regex101
Build and debug regular expressions with a live explanation of every token and a step-through debugger.
CyberChef
Chain encodings, decodings, hashes and parsers together in the browser. The Swiss army knife for data you did not create.
transform.tools
Convert between JSON, TypeScript, YAML, Go structs, SQL and a dozen other representations.
JSON Formatter
Pretty-print, validate and minify JSON, with the error position when it is malformed.
TableConvert
Turn CSV, Markdown tables, SQL results and spreadsheets into each other without a script.
IT Tools
A large self-hostable collection of small developer utilities — hashes, UUIDs, converters, generators.
Network & DNS
6Look up records, test TLS and check what the rest of the world sees.
MXToolbox
DNS, MX and blacklist lookups in one place. The fastest way to check whether mail will be delivered.
DNS Checker
Query a record from resolvers around the world to see how far a change has propagated.
What's My DNS
Global DNS propagation checker covering A, AAAA, CNAME, MX, TXT and NS.
SSL Labs Server Test
Deep TLS configuration analysis with a graded result and a specific list of what to fix.
crt.sh
Search certificate transparency logs by domain. Useful for finding subdomains you forgot existed.
Speedtest
Measure throughput and latency from the client side before blaming the server.
Development & API
7Inspect requests, decode tokens and check your shell before it runs.
crontab.guru
Translate a cron expression into plain English, or build one and see when it will next run.
explainshell
Paste a shell command and get every flag explained from the relevant man page.
ShellCheck
Static analysis for shell scripts. Catches quoting bugs and silent failures before they reach production.
jwt.io
Decode and verify JSON Web Tokens, including signature validation against a key.
Hoppscotch
Browser-based API client for REST, GraphQL, WebSocket and SSE. No install required.
httpbin
A request-and-response service for testing HTTP clients — echoes headers, delays, statuses and redirects.
ngrok
Expose a local port on a public URL. Indispensable for webhooks against a dev machine.
Design & diagrams
4Architecture diagrams, schemas and shareable snippets.
Excalidraw
Hand-drawn style diagrams that look deliberate rather than unfinished. Fast for architecture sketches.
diagrams.net
Full-featured diagramming with proper shape libraries for cloud and network topologies.
dbdiagram.io
Write a schema in a small DSL and get an entity-relationship diagram plus SQL export.
Carbon
Render a code snippet as a clean image for documentation, slides or a ticket.
Monitoring & uptime
3Watch the things that are supposed to stay up.
healthchecks.io
Cron and scheduled-job monitoring. Alerts when a job fails to check in — the gap most monitoring misses.
UptimeRobot
External uptime and response-time monitoring with a free tier that covers small deployments.
Have I Been Pwned
Check whether credentials have appeared in a breach. Worth running against every address in your organisation.
Maths & plotting
1Plot functions and surfaces, and check a curve before you trust it.
27 links across 6 categories.