encoding-formats

# Encoding & Formats

Encode, decode, and inspect data in common formats. Covers Base64, URL encoding, hex, Unicode, JWTs, hashing, checksums, and serialization formats.

## When to Use

- Decoding a Base64 string from an API response or config
- URL-encoding parameters for HTTP requests
- Inspecting hex dumps of binary data
- Decoding JWT tokens to see claims
- Computing or verifying file checksums
- Converting between character encodings (UTF-8, Latin-1, etc.)
- Understanding wire formats (protobuf, MessagePack)

## Base64

### Encode and decode

```bash
# Encode string
echo -n "Hello, World!" | base64
# SGVsbG8sIFdvcmxkIQ==

# Decode string
echo "SGVsbG8sIFdvcmxkIQ==" | base64 -d
# Hello, World!

# Encode a file
base64 image.png > image.b64
cat file.bin | base64

# Decode a file
base64 -d image.b64 > image.png

# Base64url (URL-safe variant: + → -, / → _, no padding)
echo -n "Hello" | base64 | tr '+/' '-_' | tr -d '='
# Base64url decode
echo "SGVsbG8" | tr '-_' '+/' | base64 -d
```

### In code

```javascript
// JavaScript (browser + Node.js 16+)
btoa('Hello');                    // "SGVsbG8="
atob('SGVsbG8=');                 // "Hello"

// Node.js Buffer
Buffer.from('Hello').toString('base64');           // "SGVsbG8="
Buffer.from('SGVsbG8=', 'base64').toString();      // "Hello"

// Binary data
Buffer.from(binaryData).toString('base64');
Buffer.from(b64String, 'base64');
```

```python
# Python
import base64

base64.b64encode(b"Hello").decode()     # "SGVsbG8="
base64.b64decode("SGVsbG8=")            # b"Hello"

# URL-safe Base64
base64.urlsafe_b64encode(b"Hello").decode()
base64.urlsafe_b64decode("SGVsbG8=")
```

## URL Encoding

### Encode and decode

```bash
# Python one-liner
python3 -c "from urllib.parse import quote; print(quote('hello world & foo=bar'))"
# hello%20world%20%26%20foo%3Dbar

# Decode
python3 -c "from urllib.parse import unquote; print(unquote('hello%20world%20%26%20foo%3Dbar'))"
# hello world & foo=bar

# curl does it automatically for --da...