About | DevToolKits

DevToolKits was created out of a recurring frustration familiar to most engineers: constantly switching between browser tabs to format a JSON object, decode a JWT, parse a cron expression, or convert a Unix timestamp. Each task takes only a few seconds, but the interruptions add up — and many online tools either require an account, send your data to a server, or are cluttered with distracting features.

The goal of DevToolKits is simple: provide fast, focused tools that run entirely in your browser, with no sign-up, no data collection, and no unnecessary friction. Every tool is designed around a specific task that comes up regularly during development.

What DevToolKits Covers

The toolkit is organized around the data formats and operations that appear most often in backend and full-stack development:

✓
JSON: Format, validate, minify, and convert JSON to TypeScript types, Zod schemas, OpenAPI specs, YAML, or CSV.
✓
Authentication & Security: Decode and verify JWT tokens, generate JWKS key pairs, hash data with SHA-256 and HMAC — all client-side.
✓
SQL: Format raw SQL, generate ER diagrams from CREATE TABLE statements, and build SELECT/INSERT queries visually.
✓
Time & Scheduling: Convert Unix timestamps to human-readable dates, translate between UTC and local timezones, and parse cron expressions.
✓
Encoding: Encode and decode Base64, Base58, and Base32. Encode and decode URLs.
✓
Text & Diff: Compare two text blocks side-by-side with syntax highlighting, generate Markdown tables from spreadsheet data.
✓
Infrastructure: Visualize GitHub Actions workflows and generate infrastructure diagrams from simple text notation.

Design Principles

Privacy by default

Tool input is processed in the browser. Data you paste or type is not sent to any server. You can verify this by opening your browser's network tab.

No account required

Every tool is available immediately, without registration, login, or any form of sign-up.

Single-purpose focus

Each tool does one thing well. No feature bloat, no dashboards, no settings to configure before you can start working.

Works on any device

All tools are responsive and work on desktop, tablet, and mobile. No installation or browser extension needed.

Operation

DevToolKits.app is an independent project designed, built, and maintained by a working software engineer. Every tool here started as something the maintainer personally needed during day-to-day development — API debugging, data conversion, authentication, infrastructure — and is implemented around tasks that recur in real engineering work. There is no corporate funding or investor roadmap; the project is guided by a single question — "Is this a tool I would want to use every day?" — with accuracy and privacy as the top priorities.

Technical articles by the maintainer (Zenn)

Transparency (Ads & Funding)

Running this site is supported by advertising revenue, including Google AdSense. Ads never limit tool functionality, and the data you enter into tools is never sent to advertisers. For details on how ads, analytics, and data are handled, please see our Privacy Policy.

Feedback and Contributions

If you encounter a bug, notice incorrect output from a tool, or have a suggestion for a new tool or improvement, you are welcome to send it. Detailed bug reports (steps to reproduce, browser version, input data) are especially helpful. All feedback is read and used to improve the tools, though please note that individual replies are not guaranteed.

About DevToolKits