Base64 / URL / HTML Encoder

Encode or decode text instantly — nothing leaves your browser.

Plain text
Max 10 MB 0 B
Base64-encoded output 0 B
Related tools JWT Decoder JSON Formatter Text Compare

How common characters are encoded

Common characters compared across URL and HTML encoding
CharacterURL-encodedHTML entity
Space%20 (or + in query strings) 
&%26&
<%3C&lt;
>%3E&gt;
"%22&quot;
'%27&#39;
/%2Fnot encoded
?%3Fnot encoded
#%23not encoded
%%25not encoded

Base64 has no per-character mapping — it re-encodes every byte of the input, so it isn't shown in this table.

Why Use This Tool?

  • Three encodings, one page — Base64, URL and HTML
  • Encode and decode both directions, instantly
  • Swap direction and re-run on the same text in one click
  • Clear errors for invalid Base64 or malformed percent-encoding
  • Runs entirely in your browser

Features & Supported Capabilities

  • Base64 encode/decode with full Unicode support
  • URL percent-encoding via encodeURIComponent/decodeURIComponent
  • HTML entity encode/decode for the five structural characters
  • Nothing is ever uploaded — conversion happens locally
  • Copy the result in one click

About this Base64, URL and HTML encoder / decoder

Encoding turns data into a form that can be safely stored or sent. This free online tool encodes and decodes three common formats: Base64 for embedding binary or text in JSON, headers and emails; URL (percent) encoding for query strings and paths; and HTML entities for displaying special characters safely in web pages.

Results are instant and everything runs in your browser, so nothing you paste is uploaded. Related tools: the JWT decoder for Base64URL-encoded tokens and the JSON formatter.

Frequently Asked Questions

Everything you might want to know about the online Base64 / URL / HTML encoder.

Base64 turns arbitrary bytes into plain ASCII text, commonly used to embed binary data (images, files) in text formats like JSON or HTML. URL encoding makes text safe to put inside a URL by percent-escaping reserved characters. HTML encoding escapes characters that would otherwise be parsed as markup when displayed in a web page.
No. Base64 is a reversible encoding, not encryption — anyone can decode it back to the original text with no secret required. Never use it to protect sensitive data.
Base64 only uses letters, digits, +, / and = padding. Any other character, or a length that isn't a multiple of 4 once padding is accounted for, means the text isn't valid Base64.
This tool encodes spaces as %20, the standard percent-encoding used in URL paths. Query strings traditionally also accept + for spaces, but %20 is universally valid everywhere a URL component can appear.
The five characters that matter for safely displaying text inside HTML markup: &, <, >, " and '. Other characters, including non-ASCII text, are left as-is.
Yes — all three modes are fully Unicode-aware. Base64 encodes the UTF-8 bytes of the text, and URL/HTML encoding handle any character correctly.
It flips Encode/Decode and moves the current output into the input box, so you can immediately verify a round trip or continue working the other direction.
No. All encoding and decoding runs entirely in your browser. Nothing you type here is ever sent to a server, stored, or logged.
Yes, 10 MB — the same cap used across the site. The current size of your input is shown above the input box, and pasting something larger is rejected with a clear message instead of freezing the tab.