URL Encoder or Decoder

Tools and Utilities • Digital and Web Utilities

Written by STEM Calculators Team Published December 24, 2025 Updated February 24, 2026

Choose Encode or Decode, pick the behavior (encodeURIComponent vs encodeURI), then type in the input box. Output updates live. Press Calculate to reveal the diff-like view and the query-string parser.

Mode Behavior —

Input

— Ready

Output (live)

— —

Simple rule: encodeURIComponent is best for individual parameter values. encodeURI is best for full URLs because it keeps reserved characters like :, /, ?, &, #.

Diff + Query parser hidden

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How to use the URL Encoder / Decoder

1) Choose the mode

Encode: converts special characters into percent-escapes (for safe URLs).
Decode: converts percent-escapes back into readable characters.

2) Choose the behavior

encodeURIComponent / decodeURIComponent: best for individual pieces like query parameter values.
encodeURI / decodeURI: best for full URLs because it keeps reserved URL characters (like :, /, ?, &, #).

3) Type or paste into the Input box

The Output updates live as you type. Use Copy to copy either box. Use Swap to move output back into input.

4) Reveal the diff and query parser

Click Calculate to show the diff-like view that highlights what changed (for example, spaces becoming %20).
If a query string is detected (like ?a=1&b=2), the bonus table appears with editable key/value rows.
Use Rebuild query to generate a new query string from the table.
Use Apply to input to replace the detected query portion (or set the input to the rebuilt query if the input is query-only).

5) Reset

Press Reset to clear the calculator and hide the diff and query parser.

URL Encoder or Decoder

Input

Output (live)

Diff-like view (what changed)

Original

Transformed

Query string parser (bonus)

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