URL encoder and decoder

Percent-encode text for a URL or read it back, with the three schemes that actually differ and a list handled line by line.

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How to encode and decode a URL

1
Paste your text or a list of URLs
One value or fifty, one per line. A .txt file works too, and UTF-8 or Windows-1251 are both read.
2
Pick encode or decode and a scheme
Component for a single value, full URI for a whole address, form-urlencoded for a POST body.
3
Copy the result
Copy it straight out or download it as a text file, with the line structure preserved either way.

Three schemes, and why picking wrong breaks links

Component encoding escapes everything that is not unreserved, including : / ? # & =. That is correct for a single value going into a query string, and wrong for a whole address: encode https://example.com/a?b=1 as a component and every structural character becomes a percent sequence, leaving a string that is no longer a URL. Full-URI encoding leaves those structural characters alone and escapes only spaces and non-ASCII, which is what you want when the input is already a complete address. Form-urlencoded is component encoding plus one substitution: spaces become plus signs, as required by the format HTML forms post in.

The plus sign is genuinely ambiguous

In a form-urlencoded body, + means a space. In a path segment, + means a literal plus. Decoding cannot tell the two apart from the string alone, which is why it is a setting rather than a guess: choose form-urlencoded, or turn on plus-as-space, and pluses become spaces; leave it off and they stay. Encoding has a related trap in the other direction: a literal + in the input must become %2B before spaces are turned into pluses, or a round trip through the encoder silently converts it to a space. That ordering is fixed here, so encode then decode always returns exactly what you started with.

Broken escapes, named precisely

A lone % that is not followed by two hex digits, or a multi-byte sequence cut short like %E0%A4, makes a string undecodable, and the browser's own decoder throws an exception without saying where. Strict mode reports the line and position of the first problem so you can find it in a long list; lenient mode treats an unpaired % as a literal percent sign and returns the rest, which is usually what you want when the input is a log line rather than a real URL. Working line by line matters for the same reason: a single bad entry in a list of fifty tells you which one it was.

Text stays in this tab

The conversion uses the browser's built-in encoding functions and runs entirely locally. Query strings routinely carry tokens and identifiers, so it is worth stating plainly: nothing is uploaded, logged or retained.

Frequently asked questions

What is the difference between encodeURI and encodeURIComponent?

encodeURIComponent escapes the structural characters : / ? # & = as well, which is right for a single value inside a query string. encodeURI leaves them intact, which is right when the input is a complete address you only need to make safe.

Why does + sometimes mean a space?

Because the form-urlencoded format used by HTML form posts defines it that way. Elsewhere in a URL, + is a literal plus. Since the string alone does not say which applies, decoding offers it as an explicit choice.

What do I do about an invalid percent-encoding error?

The message names the line and position of the first broken escape, usually a lone % that should have been %25, or a truncated multi-byte sequence. Fix it, or switch to lenient decoding to get the rest of the text back.

Does it work on a list of URLs?

Yes, and that is the default. Each line is converted independently, empty lines stay empty, and line breaks are never escaped, so a list goes in and a list comes out.

Are line breaks preserved?

In per-line mode they are, including a trailing newline. Turn per-line off and the whole input is treated as one value, so its own line breaks become %0A inside the result.

How do I decode Cyrillic in an address?

Paste it and decode with the component scheme. Percent-encoded UTF-8 such as %D0%BF%D1%80%D0%B8 is turned back into the original letters; the round trip is lossless in both directions.