Base64 · URL · HTML encoder

Base64, URL percent-encoding, and HTML entity encoding are the three formats text passes through whenever it has to survive a transport that wasn't built for it. Base64 turns raw bytes into ASCII that fits into email bodies, JWT segments, data URIs, and basic auth headers. Percent-encoding (RFC 3986) is what every browser does to URL paths and query strings so reserved characters like ?, &, and space don't change a request's shape. HTML entities are how <, >, &, and " reach a browser as displayed text instead of markup.

This tool is the bidirectional pocket reference for all three. Paste a string, pick a tab, and the encoded or decoded form updates as you type — nothing leaves the browser. Common reaches: debugging a JWT payload, hand-crafting a data:URI, escaping a query parameter, sanity-checking a value that's been encoded twice. Each tab exposes the variants you meet in the wild: URL-safe Base64, encodeURI vs encodeURIComponent, named vs numeric HTML refs. The full explainer covers how each format originated and which pitfalls bite in production.