CapyToolkit
Always free, zero-cloud developer tools, hardware testers...
Developer Tools·Design Tools·Productivity·Music·Gaming
What is CapyToolkit?
CapyToolkit (capytoolkit.com) is a growing library of free utility tools that run entirely in your browser. The mission is simple: build a place you can bookmark once and rely on for years. No accounts. No logins. No paywalls. No "sign up to continue."
36 tools are live today, 18 more are in active development, and the backlog keeps growing.
What's in the library
- Hardware & Display Diagnostics: Monitor & Display Test Suite, Input Lag & Mouse Polling Rate Tester, Webcam A/V Sync & Latency Meter, webcam lighting analyzer, MIDI keyboard tester, gamepad drift tester, and more...
- Developer Parsers & Encoders: SQL Data Workbench (DuckDB-WASM, queries Parquet/Arrow/Avro/CSV/Excel locally), Big Log Explorer for 500 MB+ files, JWT Decoder, prompt token counter, cron parser, hash generator, base64 encoder, and more...
- Security & Privacy: PII Scrubber for cleaning prompts before pasting into AI, EXIF & Image Metadata Scrubber, Browser Fingerprint Inspector, offline OCR document redactor, X.509 certificate inspector, cloud config sanitizer, file hash verifier, and more...
- Audio & Acoustic Testing: Speaker Frequency Sweep & Resonance Tester, Microphone Quality, Noise & Latency Tester, Decibel Calculator, with more on the way...
- Math & Engineering Calculators: Resistor Color Code Calculator, Ohm's Law Calculator, Engineering Unit Converter, electricity unit converter, aspect ratio calculator, and more...
- Text Analysis & Converters: Readability Analyzer, Case Converter, with a reading time calculator and a Markdown preview coming soon...
- Web Design & CSS: Color Format Converter, with a WCAG contrast checker and a CSS gradient builder coming soon...
- Network & Web Reference: IPv4 / IPv6 Subnet & CIDR Calculator, P2P Network Tester, IndexNow URL Submitter, URL parser, HTTP status code reference, and more...
Browse the full tool catalog to see everything that's live and what's in development.
How it works
Tools run locally in your browser tab. The site installs as a PWA, so once it's cached the whole catalog is available offline. Treat it like local software you happen to launch from a URL.
Where to follow updates
- Homepage: capytoolkit.com
- Blog: capytoolkit.com/blog/
- Reddit: reddit.com/user/CapyToolkit/
- X: x.com/CapyToolkit
- GitHub: github.com/capytoolkit
- Bluesky: bsky.app/profile/capytoolkit.com
Support the project
- Buy me a watermelon: buymeacoffee.com/capytoolkit
Feedback, bug reports, and tool requests are welcome. Drop them in the comments or on any of the channels above.
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FounderPlaybooks.
What other founders did to grow.
2722 dispatches from hundreds of founders, pulled from the week's best podcasts.
I have 100 Feather customers, so what can I build for them? Everyone has a blog, so I thought why not build a chatbot that can answer everything that is on their blog. While I was building it I realized why should I limit this to 100 people. I took 2 weeks from idea to launch.
Shipped SiteGPT in two weeks by carving a chatbot out of an existing customer base
Bhanu spotted the AI wave on Twitter, scoped a chatbot for his existing Feather customers' blogs, then realized mid-build it deserved to be its own product. Starting from a known audience and a single narrow use case compressed idea-to-launch into two weeks and hit $10K MRR in month one.
We have a monthly subscription. We have a weekly and we have [yearly] with a trial as well.
Run A Weekly Plus Monthly Plus Trial-Annual Paywall To Catch Every Commitment Tier
Stoppr monetizes 13-25 year old women with a three-tier paywall: weekly, monthly, and annual-with-trial. Converting ~1.5% of 60K downloads into 900 paying subs at this mix drives $12K/mo — the weekly catches impulse buyers, the trialed annual locks in committed quitters.
There's a play for whatever you're stuck on.
Read all 2722 playbooks