Utilities for everyday development
Developers paste tokens, API responses, customer records and configuration into online tools every day, often without thinking about where that data goes. A JWT can carry user details, a JSON payload can contain personal data, and a hash input might be a secret. The developer tools here are built so that this kind of data stays in the browser tab.
They are grouped into data and code (formatters, validators, type generators, regular expressions), encoding and security (Base64, JWT, hashes, UUIDs, passwords), design (gradients, shadows, palettes, icons), time and scheduling (cron expressions, Unix timestamps) and web and SEO checks.
Browser tools and server tools
Most of these tools are pure functions that run in your browser with no network requests at all. A few need the internet by nature: checking a website's SEO or Open Graph tags means fetching that public page, a DNS lookup has to query DNS, and a mock API has to be hosted somewhere. Those tools are labelled "Processed on our server" on their pages, state what they send and what is kept, and only ever fetch the public URLs you enter.
Standards and accuracy
The tools follow the relevant specifications: JSON parsing reports the exact line and column of an error, JWT verification supports HMAC, RSA and ECDSA signatures, hashes are computed with the Web Crypto API where the browser provides it, and UUIDs come from a cryptographically secure random source. Where behaviour differs between environments, such as regular-expression flavours or SQL dialects, the tool says which one it uses.
Working safely with sensitive data
Treat tokens, keys and production data as secrets even in a local tool: close the tab when you are done and avoid pasting them into tools that send data to a server. For checks that must fetch a URL, use public pages only; the server tools refuse private and internal network addresses, which also protects you from accidentally probing your own network.