Base64 Decoder

Turn Base64 or Base64URL strings into UTF-8 text. Paste an encoded segment and click Run — handy for JWT payloads and API responses. Binary data may show replacement characters.

  • Runs entirely in your browser
  • No data stored or sent to a server
  • Free forever — no signup
  • Instant conversion

Input and Output

Use the interactive encoder and decoder on this page to process your text.

Learn more about Base64 decoding

How to Decode Base64 Back to Text (With Examples)

Base64 Decoding

When to Decode Base64

Decode Base64 when inspecting JWT payloads, debugging API responses, reading encoded email parts, or converting data URIs back to readable content.

Real-World Examples

SGVsbG8= → Hello

dXNlcjpwYXNz → user:pass

JWT middle segment (payload) is Base64URL-encoded JSON — decode to inspect claims

Common Mistakes

  • Leading or trailing whitespace and surrounding JSON quotes are stripped automatically — other stray characters may still cause decode failures
  • Confusing Base64 with Base64URL — this decoder accepts both; full JWT tokens are easier to inspect with the JWT Decoder tool
  • Expecting decoded output to always be readable text — it may be binary gibberish if the source was not text

Edge Cases

  • Invalid characters (outside the Base64 alphabet) cause decode failures
  • Missing padding can break strict decoders — some libraries add padding automatically
  • Decoded bytes may require UTF-8 interpretation for non-English text

Developer Tips

  • Browser: atob() returns a binary string; combine with TextDecoder for Unicode
  • Always validate decoded content before using it in security-sensitive paths

Frequently asked questions

Why does decoding fail with an invalid character error?

The input likely contains characters outside the Base64 alphabet, PEM headers, or other stray text. Standard and URL-safe Base64 are both accepted — quotes and padding are normalized automatically.

Is decoded Base64 always readable text?

No. If the original data was binary, decoded output may not be human-readable text.

Can I decode JWT tokens here?

You can decode individual Base64URL segments (header or payload). For a full JWT with signature verification context, use the JWT Decoder tool.