Online URL encoder and decoder tool. Supports URI component encoding (encodeURIComponent) and full URL encoding. Processed locally in your browser.
TL;DR: Free online URL encoder/decoder with Component or Full URI mode, space-as-+, lenient decode, and peel-all-layers. Runs locally in your browser.
For local tools, open DevTools → Network and search your input — it should not appear in requests.
Next steps
Usage Guide
URLs admit only a subset of ASCII: Chinese characters, spaces, &, = and # either lose their meaning or break the link outright when concatenated raw. This tool offers Component (encodeURIComponent) or Full URI (encodeURI) mode, plus encode “space as +”, decode “+ as space”, lenient keep-invalid-%, and peel-all-layers — fully locally.
1. Encode and decode
Strict decode (default) raises URIError on a lone % (e.g. literal 100%). Lenient keeps invalid fragments while still decoding valid %HH runs — handy for half-cut strings from logs.
- Pick Component (param/path segment) or Full URI (whole address; keeps :/?#&=).
- Encode: spaces become %20 by default; enable “space as +” for form/query habit.
- Decode: enable “+ as space” for form strings; “lenient” for truncated logs; “peel all layers” when you suspect double encoding (layer count shown beside output).
- Copy and substitute into your link or code.
2. encodeURI or encodeURIComponent
encodeURI keeps URL structure characters and suits whole URLs; encodeURIComponent encodes & = / too and suits values. The page mode switch maps to these two APIs. Rule: whole link → Full URI; parameter values → Component.
3. Three frequent traps
- Spaces: %20 vs +. Use “space as +” on encode and “+ as space” on decode as a matching pair.
- Double encoding: %2520 is %20 encoded again. Peel-all-layers restores it and reports the depth (2 = encoded twice).
- Unencoded specials in param values break links intermittently.
4. Boundaries of this tool
Default Component writes spaces as %20; form-style + only when the encode toggle is on. Decode leaves + alone and throws on malformed % unless those toggles are enabled. Full URI uses encodeURI/decodeURI. For structured split/rebuild use url-parser / url-params-parser.
5. Encoding chains for CJK and special characters
- 中 → %E4%B8%AD (three UTF-8 bytes).
- In form-urlencoded, + means space; under default decode, + is a plus.
- Repeated %25 prefixes — or peel depth ≥ 2 — usually mean double encoding.
6. Form encoding vs path encoding vs query strings
Three situations get lumped under “URL encoding”: spaces/CJK in path segments (almost always %20 / UTF-8 percent-encoding), query parameter values (%20 or legacy form +), and application/x-www-form-urlencoded bodies (where + means space by spec). This page’s Component / Full URI modes separate “encode one value” from “encode a whole URI”; space-as-+, +-as-space, lenient, and peel-layers are debugging switches, not default production policy. For structured add/remove of params, switch to the URL params parser instead of hand-editing & in a string.
7. Checklist when encoding still yields HTTP 400
- Locate the layer: address bar, reverse-proxy logs, or the app’s query parser — each may encode or decode again.
- JSON in a query must be Component-encoded as a whole; encoding only inner CJK while leaving braces raw splits on &.
- Runs of %25 in logs: peel to see depth, then decide whether the gateway double-encoded or the client called encode twice.
- Full URI mode will not encode existing ?&=; if your “full URL” is actually a callback value destined for a parameter, use Component.
- IDN hostnames may display as Unicode in the browser but travel as xn-- Punycode on the wire — this page handles percent-encoding of paths/params, not IDN ↔ Punycode conversion.
FAQ
It depends on whether you are encoding a value or a whole address: encodeURIComponent encodes / ? : & = too, which is right for parameter values; encodeURI preserves URL structural characters for complete links. The page's Component / Full URI modes map to these two semantics. One rule of thumb: full links take Full URI, parameter values always take Component.
RFC percent-encoding uses %20; application/x-www-form-urlencoded (form submissions and many query parsers) uses +. The tool outputs %20 by default and produces form style only with “encode space as +” enabled; on the decode side + stays literal unless “treat + as space” is on. Read the two switches as a pair.
%2520 is a space encoded twice (%20 encoded again); enable “peel all layers” to restore it in one go and see how many layers there were. A lone % (as in the literal 100%) throws a URIError in the strict default mode — with “lenient” on, invalid fragments stay untouched while valid %HH runs still decode, which suits half-truncated strings pulled from logs.
Check three layers: JSON in a query string must be Component-encoded as a whole — encoding only the Chinese inside while leaving braces naked gets chopped at the first &; repeated %25 runs in logs mean double encoding, so peel to see the depth and find whether the gateway or the client encoded twice; and Full URI mode never encodes existing ?&=, so switch to Component when a whole URL is itself a parameter value.
URL standards allow only an ASCII subset, so 「中」 must become its UTF-8 percent form %E4%B8%AD (three bytes, three %XX triplets) to travel correctly. Chinese domain names are a separate matter: browsers display Unicode while the wire carries xn-- Punycode. This page handles percent-encoding, not IDN/Punycode conversion.
Nowhere at all. Encoding, decoding, and layer-peeling in every mode run locally in your browser — the link never leaves your device.
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