Encode Base64 Data in a QR Code

QR Codes for Base64 Data

Base64 encoding converts binary data into ASCII text, making it compatible with QR codes. This enables QR codes to carry binary payloads like small files, cryptographic keys, or compressed data.

Why Base64 in QR Codes?

QR codes store text data. To embed binary content, you need a text-safe encoding:

• Base64 — Standard encoding, 33% size overhead
• Base64url — URL-safe variant, replaces +/ with -_, no padding

Encoding a Small File

For a small configuration file or certificate:

data:application/json;base64,eyJrZXkiOiJ2YWx1ZSIsIm51bSI6NDJ9

The receiving application decodes the Base64 string back to binary:

const decoded = atob("eyJrZXkiOiJ2YWx1ZSIsIm51bSI6NDJ9");
// Result: {"key":"value","num":42}

Size Constraints

Base64 has a 33% overhead — 3 bytes of binary become 4 characters of Base64 text. Combined with QR code capacity limits:

QR Version	Error Correction M	Binary Capacity	Base64 Capacity
10 (57x57)	~652 chars	~489 bytes	~652 chars
20 (97x97)	~1,460 chars	~1,095 bytes	~1,460 chars
40 (177x177)	~3,391 chars	~2,543 bytes	~3,391 chars

Practical Limit

For reliable scanning with a phone camera, stay within QR Version 15-20 (about 1,000-1,500 Base64 characters). Larger codes require high-resolution printing and close scanning distance.

Data URI Format

Combine Base64 with Data URIs for self-describing payloads:

data:<mediatype>;base64,<data>

Common media types:

• application/json — Configuration data
• application/x-pem-file — Certificates
• application/octet-stream — Generic binary

Use Cases for Base64 QR Codes

1. Certificate distribution — Share small X.509 certificates or public keys
2. Compressed data — Gzip-compress JSON, then Base64-encode the result
3. Small images — Encode tiny icons or avatars (under 1KB)
4. Encrypted payloads — AES-encrypted data encoded as Base64
5. Configuration blobs — Device settings in a compact binary format