How do I encode Base64 without newlines in bash?

Use base64 -w 0: echo -n 'text' | base64 -w 0. The -w 0 flag disables line wrapping and produces a single continuous Base64 string with no newline characters. This is essential when embedding Base64 in JSON or HTML.

Linux Base64 Decode & Encode — bash Command Guide

How Do You Encode Base64 on Linux?

The base64 command is part of GNU coreutils and is available on all Linux distributions. To encode a string, pipe it to base64. Use echo -n to avoid including the trailing newline in the encoded output:

echo -n 'Hello World' | base64
# Output: SGVsbG8gV29ybGQ=

# Wrong — includes the newline character in encoding
echo 'Hello World' | base64
# Output: SGVsbG8gV29ybGQK  (different result — K at end encodes the newline)

How Do You Decode Base64 on Linux?

Use the -d flag to decode. On Linux (GNU base64), the flag is lowercase -d. On macOS (BSD base64), the flag is uppercase -D:

echo 'SGVsbG8gV29ybGQ=' | base64 -d
# Output: Hello World

# Decode to stdout (no trailing newline added)
echo 'SGVsbG8gV29ybGQ=' | base64 --decode

How Do You Encode and Decode Files in Bash?

Use file redirection to encode or decode whole files without piping:

# Encode a binary file to Base64
base64 image.png > image.b64

# Encode and suppress line wrapping (single line)
base64 -w 0 image.png > image.b64

# Decode Base64 file back to binary
base64 -d image.b64 > decoded-image.png

# One-liner: encode file and save inline
base64 -w 0 certificate.pem > certificate.b64

How Do You Disable Line Wrapping in bash?

By default, GNU base64 wraps output at 76 characters per line (MIME format). Use -w 0 to produce a single continuous line — required when embedding Base64 in JSON, HTML, or environment variables:

# Single-line output (required for JSON/HTML embedding)
echo -n 'Hello World' | base64 -w 0
# Output: SGVsbG8gV29ybGQ=  (no line breaks)

# Kubernetes secret value (must be single line)
kubectl create secret generic my-secret \\
  --from-literal=password=$(echo -n 'mypassword' | base64 -w 0)

How Do You Use Base64 in bash Scripts?

Base64 encoding is commonly used in bash scripts for API authentication, Kubernetes secrets, and embedding binary assets:

#!/bin/bash

# Basic Auth header for API calls
USERNAME="admin"
PASSWORD="secret"
CREDENTIALS=$(echo -n "$USERNAME:$PASSWORD" | base64 -w 0)
curl -H "Authorization: Basic $CREDENTIALS" https://api.example.com/data

# Encode a file as a variable
IMAGE_B64=$(base64 -w 0 logo.png)
echo '{"image": "'"'"'$IMAGE_B64'"'"'"}' | curl -X POST -d @- https://api.example.com/upload

# Decode a secret from an environment variable
echo "$BASE64_SECRET" | base64 -d > /tmp/secret.key

Linux vs macOS Base64 Commands — Key Differences

Operation	Linux (GNU)	macOS (BSD)
Encode string	`echo -n 'str' \| base64`	`echo -n 'str' \| base64`
Decode string	`echo 'b64' \| base64 -d`	`echo 'b64' \| base64 -D`
No line wrap	`base64 -w 0`	`base64 -b 0`
Encode file	`base64 file.bin`	`base64 -i file.bin`
Decode file	`base64 -d file.b64`	`base64 -D -i file.b64`

For macOS-specific usage see the Base64 on Mac guide. For browser-based encoding without a terminal, use the Text Encoder or File Encoder.

Frequently Asked Questions

How do I encode Base64 on Linux?

Run echo -n 'text' | base64. For files: base64 file.bin > file.b64. Use -w 0 to disable line wrapping.

How do I decode Base64 on Linux?

Run echo 'BASE64' | base64 -d. For files: base64 -d input.b64 > output.bin.

Why does base64 -d not work on Mac?

macOS uses -D (uppercase). Linux uses -d (lowercase). See the macOS Base64 guide for Mac-specific commands.

How do I Base64 encode without newlines in bash?

Use base64 -w 0: echo -n 'text' | base64 -w 0. This produces a single continuous string, required for JSON embedding and Kubernetes secrets.