When base64 wraps JSON
APIs sometimes base64-encode JSON bodies for transport or storage. base64app decodes the bytes, detects UTF-8 JSON text, and shows a readable preview.
How it works
- 1. Paste the base64 string above.
- 2. Click Decode — if the payload is JSON text, a preview appears.
- 3. Download as .json or copy the decoded text.
Common errors
- Invalid characters — standard base64 only uses A–Z, a–z, 0–9, +, /, and = padding.
- Missing or wrong padding — length should be a multiple of 4; add = at the end if needed.
- Line breaks and spaces — email, Slack, and JSON often insert whitespace that must be stripped.
- data: URI prefix left on the string — remove data:<mime>;base64, before decoding.
- URL-safe alphabet — JWTs and some APIs use - and _ instead of + and /.
- Truncated payload — a copied string cut off mid-way cannot be fully recovered.
- Binary JSON (BSON) — this tool decodes UTF-8 text JSON, not binary BSON payloads.
- Double encoding — JSON may be wrapped in quotes and encoded twice; decode once and inspect.
Frequently asked questions
How do I decode base64 to JSON?
Paste and Decode. When bytes are UTF-8 JSON, base64app shows a text preview and .json download.
Will it pretty-print JSON?
The preview shows decoded text. You can copy it into any JSON formatter.
What if decode shows binary?
The string may encode a file, not JSON text. Check detectedType in the result.
Is API data stored?
No. Decoding is entirely local.
Is my data uploaded when I decode?
No. All processing runs in your browser. Nothing is uploaded, stored, or logged.
Can base64app fix corrupted base64?
Yes. Auto-repair fixes whitespace, data URI prefixes, URL-safe characters, padding, and stray characters.