# Base64 Encoding > Encoding and decoding utilities — base64, URL encoding, hex, and hashing. Use when user mentions "base64", "encode", "decode", "url encode", "urlencode", "hex", "hash", "sha256", "md5", "checksum", "jwt decode", "binary to text", or converting between encoding formats. - Skill: `1mangesh1/base64-encoding` (Agent Skill) - Install (CLI): `npx skillmds@latest add 1mangesh1/base64-encoding` - Raw SKILL.md: https://api.skillmd.com/api/skills/1mangesh1/base64-encoding/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: 1Mangesh1 (https://skillmd.com/u/1mangesh1) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/1mangesh1/base64-encoding --- # Encoding and Decoding Utilities ## Base64 Encode/Decode ### String ```bash # Encode echo -n 'hello world' | base64 # Decode (macOS) echo 'aGVsbG8gd29ybGQ=' | base64 -D # Decode (Linux) echo 'aGVsbG8gd29ybGQ=' | base64 -d ``` ### File ```bash # Encode a file base64 < input.bin > output.b64 # Decode to file (macOS) base64 -D < output.b64 > restored.bin # Decode to file (Linux) base64 -d < output.b64 > restored.bin ``` ### Stdin pipe ```bash curl -s https://example.com/image.png | base64 ``` ### macOS vs Linux | Operation | macOS | Linux | |-----------|----------------|----------------| | Decode | `base64 -D` | `base64 -d` | | Wrap cols | `base64 -b 76` | `base64 -w 76` | Portable: `base64 --decode 2>/dev/null || base64 -D` ## URL Encoding/Decoding ```bash # Python 3 python3 -c "import urllib.parse; print(urllib.parse.quote('hello world&foo=bar'))" python3 -c "import urllib.parse; print(urllib.parse.unquote('hello%20world%26foo%3Dbar'))" # Node.js node -e "console.log(encodeURIComponent('hello world&foo=bar'))" node -e "console.log(decodeURIComponent('hello%20world%26foo%3Dbar'))" ``` ## Hex Encode/Decode ```bash # String to hex echo -n 'hello' | xxd -p # Output: 68656c6c6f # Hex to string echo '68656c6c6f' | xxd -r -p # Output: hello # File to hex dump xxd input.bin # Compact hex (no formatting) xxd -p input.bin # Using od echo -n 'hello' | od -A n -t x1 | tr -d ' \n' # Hex to bytes with printf printf '\x68\x65\x6c\x6c\x6f' ``` ## Hashing ### String hashing ```bash # MD5 echo -n 'hello' | md5sum # Linux echo -n 'hello' | md5 # macOS # SHA-1 echo -n 'hello' | sha1sum # Linux echo -n 'hello' | shasum -a 1 # macOS # SHA-256 echo -n 'hello' | sha256sum # Linux echo -n 'hello' | shasum -a 256 # macOS # SHA-512 echo -n 'hello' | sha512sum # Linux echo -n 'hello' | shasum -a 512 # macOS ``` Use `echo -n` to avoid hashing the trailing newline. ### File hashing ```bash sha256sum myfile.tar.gz # Linux shasum -a 256 myfile.tar.gz # macOS ``` ### OpenSSL (cross-platform) ```bash openssl dgst -sha256 myfile.tar.gz echo -n 'hello' | openssl dgst -sha256 ``` ## Verify File Integrity with Checksums ```bash # Generate checksum file sha256sum release.tar.gz > release.sha256 # Verify (Linux) sha256sum -c release.sha256 # Verify (macOS) shasum -a 256 -c release.sha256 # Quick inline comparison EXPECTED="e3b0c44298fc1c149afbf4c8996fb924..." ACTUAL=$(sha256sum downloaded.tar.gz | awk '{print $1}') [ "$EXPECTED" = "$ACTUAL" ] && echo "OK" || echo "MISMATCH" ``` ## JWT Decode Without a Library A JWT has three dot-separated base64url segments: header, payload, signature. ```bash JWT="eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkwIn0.dozjgNryP4J3jVmNHl0w5N_XgL0n3I9PlFUP0THsR8U" # Decode header echo "$JWT" | cut -d. -f1 | tr '_-' '/+' | base64 -d 2>/dev/null || \ echo "$JWT" | cut -d. -f1 | tr '_-' '/+' | base64 -D # Decode payload echo "$JWT" | cut -d. -f2 | tr '_-' '/+' | base64 -d 2>/dev/null || \ echo "$JWT" | cut -d. -f2 | tr '_-' '/+' | base64 -D ``` Base64url uses `-` and `_` instead of `+` and `/`. The `tr` call converts back. Add padding if needed: ```bash decode_b64url() { local d="$1" pad=$(( 4 - ${#1} % 4 )) [ "$pad" -lt 4 ] && d="${d}$(printf '%0.s=' $(seq 1 $pad))" echo "$d" | tr '_-' '/+' | base64 -d 2>/dev/null || echo "$d" | tr '_-' '/+' | base64 -D } decode_b64url "$(echo "$JWT" | cut -d. -f2)" ``` ## Generate Random Strings ```bash # Alphanumeric, 32 chars cat /dev/urandom | LC_ALL=C tr -dc 'a-zA-Z0-9' | head -c 32 # Hex string, 32 chars openssl rand -hex 16 # Base64 string openssl rand -base64 24 # URL-safe random string openssl rand -base64 32 | tr '+/' '-_' | tr -d '=' # UUID-like cat /proc/sys/kernel/random/uuid 2>/dev/null || uuidgen ``` ## HTML Entity Encode/Decode ```bash # Encode (Python) python3 -c "import html; print(html.escape('
&
'))" # Output: <div class="x">&</div> # Decode (Python) python3 -c "import html; print(html.unescape('<div>hello</div>'))" # Decode (Perl) perl -MHTML::Entities -e 'print decode_entities("<p>hello</p>")' ``` ## Unicode Escape/Unescape ```bash # Unescape \uXXXX sequences (Python) python3 -c "print('\\u0048\\u0065\\u006c\\u006c\\u006f')" # Escape string to \uXXXX python3 -c "print(''.join(f'\\\\u{ord(c):04x}' for c in 'Hello'))" # Unescape JSON unicode (jq) echo '"\\u0048\\u0065\\u006c\\u006c\\u006f"' | jq -r . # UTF-8 hex bytes to character printf '\xc3\xa9' # prints: e with accent (é) # Character to UTF-8 hex echo -n 'é' | xxd -p ``` ## Common Patterns ### Encode a file for JSON embedding ```bash BASE64=$(base64 < image.png | tr -d '\n') echo "{\"image\": \"data:image/png;base64,${BASE64}\"}" ``` ### Decode a base64 field from an API response ```bash curl -s https://api.example.com/data | jq -r '.content' | base64 -d ``` ### Verify a download checksum ```bash curl -LO https://example.com/release.tar.gz curl -sL https://example.com/release.sha256 | sha256sum -c - ``` ### Generate an API key ```bash openssl rand -base64 32 | tr -d '\n' openssl rand -hex 32 ``` ### Encode credentials for Basic Auth ```bash echo -n 'user:password' | base64 # Use in header: Authorization: Basic dXNlcjpwYXNzd29yZA== ``` ## Quick Reference | Task | Command | |-----------------------------|--------------------------------------------------| | Base64 encode string | `echo -n 'text' \| base64` | | Base64 decode (macOS) | `echo 'data' \| base64 -D` | | Base64 decode (Linux) | `echo 'data' \| base64 -d` | | URL encode | `python3 -c "import urllib.parse; print(urllib.parse.quote('...'))"` | | URL decode | `python3 -c "import urllib.parse; print(urllib.parse.unquote('...'))"` | | Hex encode | `echo -n 'text' \| xxd -p` | | Hex decode | `echo 'hex' \| xxd -r -p` | | MD5 hash | `echo -n 'text' \| openssl dgst -md5` | | SHA-256 hash | `echo -n 'text' \| openssl dgst -sha256` | | SHA-256 file | `openssl dgst -sha256 file.tar.gz` | | Verify checksum | `sha256sum -c checksums.sha256` | | JWT decode payload | `echo $JWT \| cut -d. -f2 \| tr '_-' '/+' \| base64 -d` | | Random hex (32 chars) | `openssl rand -hex 16` | | Random base64 | `openssl rand -base64 24` | | HTML encode | `python3 -c "import html; print(html.escape('...'))"` | | HTML decode | `python3 -c "import html; print(html.unescape('...'))"` | | Unicode unescape | `python3 -c "print('\\u0048\\u0065')"` | | Basic Auth header | `echo -n 'user:pass' \| base64` |