Security

Base64URL Decoder

Decode a Base64URL string into readable plain text.

Last reviewed: April 30, 2026Free toolMethodology

Base64URL Decoder

These fields start with sample inputs. Keep them or replace them, then run the tool to show a fresh result.

Output

Calculating the sample result.

Why it matters

Base64URL is common in tokens and web-safe payloads, and developers often need a fast decoder to inspect those values locally.

When to use

  • Inspecting JWT header or payload segments
  • Debugging URL-safe encoded values
  • Checking whether a token segment contains the expected JSON

Inputs & Outputs

Inputs

  • Input should be a valid Base64URL string, usually without padding.

Outputs

  • Decoded output restores the readable text when the input represents UTF-8 content.
  • Validation feedback helps identify malformed input.

Base64URL decoding method

The tool restores standard Base64 characters and padding where needed, then decodes the value into UTF-8 text.

Base64URL decoding reverses the URL-safe character substitutions before normal decoding

Worked example

1

JWT payload inspection

An engineer wants to decode the payload segment `eyJzdWIiOiIxMjMiLCJzY29wZSI6ImRlbW8ifQ`.

Inputs

  • Base64URL input: eyJzdWIiOiIxMjMiLCJzY29wZSI6ImRlbW8ifQ

Steps

  • Normalize to standard Base64
  • Restore padding
  • Decode to UTF-8 text

Result

  • The output reveals the original JSON payload.

Edge cases & caveats

  • Binary content may not decode into readable text.
  • Malformed padding or mixed character sets can produce decode errors.

Frequently Asked Questions

Why is this different from normal Base64 decoding?

Because Base64URL replaces reserved characters and often omits padding, which normal decoders may not accept directly.

Can I use this for JWT segments directly?

Yes. JWT segments are a common Base64URL decoding use case.

Keep going

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