Base64 → Text

Paste base64 below, get the decoded UTF-8 text. Whitespace, line breaks, and URL-safe variants all work.

How the decoder works

1. Strip whitespace (spaces, tabs, newlines).
2. Replace - with + and _ with / (URL-safe normalization).
3. Pad with = until length is a multiple of 4.
4. Run through atob() to get a binary-string of the bytes.
5. Convert to a Uint8Array and decode as UTF-8 with TextDecoder.

Steps 1–4 produce bytes; step 5 produces text. If the bytes aren't valid UTF-8, step 5 throws a "decode error" — that's usually a sign the input was binary data, not text.

Common things to decode

• HTTP Basic Auth headers. Strip the Basic prefix, paste the rest.
• JWT parts. The header and payload (first two segments) are URL-safe base64 JSON. The signature is binary — don't expect it to decode to text.
• Email attachments. The base64 body of a MIME part decodes back to the original file bytes (not text — use the file decoder).
• Kubernetes secrets. kubectl get secret X -o yaml shows base64-encoded values. Decode here to see them in plain text.
• Configuration values. Many cloud / CI systems base64-encode env vars and certs.

What "decode error" means

Two distinct failure modes:

• "Invalid character" — the input has a character outside the base64 alphabet. Common causes: a stray space, an HTML entity (&), or copy-paste artifacts. Trim and retry.
• "Invalid UTF-8" — the base64 decoded successfully but the bytes aren't a valid UTF-8 string. The input was binary (an image, audio, encrypted blob), not text. Use the file decoder to write the bytes to a file instead.

In code

// JavaScript (UTF-8 safe)
const bytes = Uint8Array.from(atob(b64.replace(/-/g,"+").replace(/_/g,"/")),
                              c => c.charCodeAt(0));
const text = new TextDecoder().decode(bytes);

// JavaScript (Node 16+)
Buffer.from(b64, "base64").toString("utf-8");
Buffer.from(b64, "base64url").toString("utf-8");

// Python
import base64
base64.b64decode(b64).decode()
base64.urlsafe_b64decode(b64 + "==").decode()  // urlsafe needs padding sometimes

// Bash
echo "$b64" | base64 -d

// Go
import "encoding/base64"
data, _ := base64.StdEncoding.DecodeString(b64)