Developer utilities
Small browser tools developers keep open: regex, shell, diagrams, code images, status checks. 11 resources; API, key, license and embedding quoted from each site's own pages, checked Oct 23, 2026.
regex101
You can watch a pattern match step by step, see why it fails, and catch catastrophic backtracking before it hits production.
API, no keyLicense unclear
Excalidraw
Diagrams look like napkin sketches, which makes architecture drawings feel friendly, and the scene file is plain JSON a program can generate.
Commercial OK
explainshell
Cryptic one-liners copied from forums turn into a readable map of what every switch actually does before you run them.
DownloadCommercial: conditions
Code Beautify
Almost any quick conversion a developer needs (JSON to CSV, XML to JSON, Base64, hashes, test data) sits one page away, with most of the work done in your browser.
License unclear
tldraw
The same engine behind a polished public whiteboard is a programmable canvas you can drive from code, shape by shape.
Commercial: conditions
Carbon
It is the tool behind many of the neat code screenshots on social media, and its whole editor is MIT-licensed code you can run yourself.
License unclear
ray.so
A fast, good-looking way to make code screenshots, and its Next.js source is public, so you can see exactly how the rendering works.
License unclear
Downdetector
When a big app or cloud service breaks, the spike in user reports shows up on its chart within minutes.
LiveAPINon-commercial
FAST.com
It tests against the same Netflix servers that stream video, and its loaded-latency figure exposes bufferbloat that simple speed tests miss.
LiveLicense unclear
Temp Mail
Handy for checking that your app's verification and password-reset emails actually arrive and render, without cluttering a real inbox.
LiveLicense unclear
10 Minute Mail
It has been running since 2006, and it's a quick way to see your app's welcome or verification email arrive end to end.
LiveLicense unclear
Side by side
| Resource | API | Key | Data download | Commercial use | Embed |
|---|---|---|---|---|---|
| regex101 A browser editor for writing, testing and debugging regular expressions in ten engine flavors, with a plain-English breakdown of each token, match details, substitution, unit tests and shareable saved versions. |
Official API · Free tier | No | — | Commercial use unclear | Embedding unclear |
| Excalidraw A free in-browser whiteboard for quick hand-drawn-style diagrams and sketches, with live collaboration and export to PNG, SVG or its JSON scene format; the editor is also an MIT React component. |
No official API | — | — | Commercial use OK | Embedding unclear |
| explainshell Paste a shell command and it splits it into parts, linking each flag and argument to the matching passage of the program's man page (Ubuntu and Arch). |
No official API | — | Yes (sqlite) | Commercial use with conditions | Embedding unclear |
| Code Beautify A large ad-supported collection of single-purpose web tools for formatting, validating, minifying and converting code and data formats such as JSON, XML, CSV, SQL and YAML. |
No official API | — | — | Commercial use unclear | Embedding unclear |
| tldraw A free online infinite-canvas whiteboard for sketches and diagrams, built on the tldraw React SDK, which developers can use to add a canvas editor to their own apps under a separate license. |
No official API | — | — | Commercial use with conditions | Embedding with conditions |
| Carbon Turns a pasted code snippet or GitHub gist into a styled image, with themes, fonts and window frames, exported as PNG or SVG or embedded as an iframe. |
No official API | — | — | Commercial use unclear | Can be embedded |
| ray.so Raycast's free web tool for turning code into polished images with syntax themes, light or dark windows and optional backgrounds, plus an icon maker and browsers for Raycast prompts, presets, snippets and themes. |
No official API | — | — | Commercial use unclear | Embedding unclear |
| Downdetector A live outage tracker that charts problem reports from users and social media for apps, websites, ISPs and mobile networks, so you can tell whether a service is down for everyone or just for you. |
Official API | Not stated | — | Non-commercial only | Embedding unclear |
| FAST.com Netflix's ad-free internet speed test that starts on page load and measures download speed, with upload speed and loaded/unloaded latency on request. |
No official API | — | — | Commercial use unclear | Embedding unclear |
| Temp Mail A disposable email inbox in the browser that gives you a throwaway address to receive mail; use it only for testing your own sign-up and email flows. |
API unclear | — | — | Commercial use unclear | Embedding unclear |
| 10 Minute Mail A short-lived disposable email address in the browser for receiving mail; use it only for testing your own sign-up and email flows. |
API unclear | — | — | Commercial use unclear | Embedding unclear |