🧰 ToolBox

ToolBox is a curated collection of 33 free, browser-first utility tools designed for the small, frequent computing tasks that show up across software development, finance, writing, study, and daily life. Every tool runs locally in your browser: nothing you paste or type is uploaded to a server, and there are no accounts, paywalls, trial limits, or feature gates. Each tool also ships with a written guide that explains how the underlying transformation or calculation works and walks through worked examples, so the page is useful whether you arrived to actually use the tool or to understand the concept behind it.

The collection is organised into five categories. Text tools cover counting, case conversion, diffing, deduplication, Lorem Ipsum, Markdown conversion, character reversal, and HTML entity encoding — the everyday string operations that writers, editors, and content engineers reach for. Developer tools focus on the small daily tasks of building and debugging software: formatting JSON, encoding Base64 and URLs, testing regular expressions, picking colours, building cron expressions and CSS gradients, generating cryptographic hashes, and decoding JSON Web Tokens. Calculators handle the numerical questions that come up in finance, health, scheduling, and study — percentages, age, tips, BMI, loan EMI with full amortisation, compound interest with monthly contributions, and date arithmetic including workdays. Generators cover identifiers, codes, and randomness for application development and everyday use. Converters handle unit conversions for length, weight, temperature, speed, and numeric bases.

Why a browser-first, privacy-first toolbox?

A lot of the “free online tools” on the open web have a quiet problem: when you paste a JWT, an API response, a password, or a piece of customer data into them, you are sending that data to someone else’s server. For most everyday utilities this is unnecessary — modern browsers can encode Base64, compute SHA-256, parse JSON, and do far more, all entirely client-side. ToolBox is built on that observation. The tools use standard Web Platform APIs (the SubtleCrypto interface for hashing, the Intl APIs for formatting, native URL and TextEncoder objects, and so on), which means your inputs never leave the page. The one exception is the QR code generator, which calls a public image API; it’s clearly labelled on the tool itself and in our Privacy Policy.

The other reason for a single toolbox is consistency. Each tool here uses the same layout, dark mode, font sizing, keyboard handling, and copy-to-clipboard behaviour, so once you’ve learned how one tool works you know how all of them work. There’s no learning curve when you move from the JSON formatter to the regex tester to the loan calculator.

Who uses ToolBox?

Developers and SREs — decoding JWTs during incident debugging, formatting log JSON, generating UUIDs for fixtures, testing regular expressions before pasting them into code review.
Students and researchers — counting words for assignments, calculating percentages and date differences, converting units in lab reports and homework.
Writers and editors — converting Markdown to HTML for newsletters, normalising case, removing duplicate lines from research notes, comparing draft revisions with the text diff tool.
Designers and front-end engineers — picking colours and reading their HEX/RGB/HSL values, building CSS gradients visually, sampling and exporting palette shades.
Anyone with a quick numerical question — splitting a restaurant bill, working out how a monthly contribution affects a 20-year investment, or just calculating their exact age in days.

How the toolbox is maintained

New tools are added regularly based on reader requests — if there’s a small utility you find yourself searching for repeatedly, please tell us via the contact page. Existing tools are reviewed for accuracy when the underlying standard changes (for example, when the WHO updates its BMI category guidance, or when a new cryptographic hash is added to the Web Crypto specification). Calculation bugs and content errors are treated as priority issues; if you spot one, please email us with the input and the result you expected and we will fix it.

ToolBox is free to use and free of dark patterns. We do not paywall any feature, ask you to sign in, sell your data, or send marketing emails. The site is partly supported by unobtrusive display advertising shown around (never on top of) the tool interfaces; if you would prefer not to see ads, any standard browser ad-blocker works fine and does not break any tool. To read more about the project and the team behind it, see the About page.