Encoder / Decoder

Encode and decode text as URL components, Base64, URL-safe Base64, and HTML entities directly in your browser, switching modes with no data sent anywhere.

Key Terms (Click to expand)

URL

Encodes text for a URL query value or path segment, converting characters such as @, spaces, ?, and &.

Base64

Represents UTF-8 text as a compact ASCII string, used for encoding rather than encryption.

Base64 URL-safe

A URL-safe Base64 variant that avoids +, /, and padding characters.

HTML entities

Numeric or named entity sequences that HTML can render back into characters.

Tool

Methodology

The encoder/decoder applies deterministic browser-safe transforms based on the selected mode.

  • URL mode encodes text for a URL query value or path segment, not a full URL document.
  • Base64 and URL-safe Base64 encode UTF-8 text bytes and decode them back to text.
  • HTML entity encoding outputs numeric entities and decoding supports numeric plus common named entities.
  • Input is processed locally in your browser.

Using This Tool Well

When to use this tool

  • Query-value encoding: encode `a+b@example.com` before putting it in a URL parameter so special characters do not change meaning.
  • Token transport check: convert text to URL-safe Base64 when standard Base64 characters like `+` and `/` would be awkward in a path.
  • HTML text safety: encode a snippet containing `<` or `&` before displaying it as text rather than markup.

How to read the result

The output is a transport transformation, not a security boundary. For a sanity check, encode a small sample, decode it in the same mode, and confirm the round trip returns the original text before applying the mode to a larger string.

Common mistakes

  • Encoding the whole URL: `https://` becomes `https%3A%2F%2F`, growing three separator characters into nine and breaking the URL shape you meant to preserve.
  • Treating Base64 as secrecy: Base64 usually expands data by about 33% and is fully reversible, so it hides 0% of the content from anyone who decodes it.
  • Mixing Base64 variants: 2 Base64 variants differ by characters such as `+`, `/`, `-`, and `_`; pasting one variant into the other mode can fail.

Reviewed by Leonardo, Software Engineer

Last reviewed June 23, 2026

Premises and Limitations

  • Encoding is not encryption and should not be treated as security protection.
  • Base64 decoding requires valid Base64 or URL-safe Base64 input for the selected mode.
  • No server-side persistence is used for encoded or decoded text.

FAQ

Which mode should I use for an email address?

Use URL encoding for URL parameters or HTML entities when you need an HTML-renderable encoded form.

Is Base64 encryption?

No. Base64 is reversible encoding and should not be used to hide secrets.

Is my text uploaded to a server?

No. Encoding and decoding run locally in your browser.

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