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Base64 Encoder / Decoder

Encode text to Base64 or decode Base64 back to plain text. Runs entirely in your browser.

By ToolHub Pro, Editorial Team — verified against NIST SP 800-63B & FIPS standards·Updated 2026-01-15

What Base64 Is and Isn't

Base64 is an encoding scheme that converts binary data into a text string using 64 printable ASCII characters (A–Z, a–z, 0–9, +, /). It was designed to safely transmit binary content through systems that only handle text. like email (MIME), embedding images in HTML/CSS via data URIs, and encoding binary data in JSON. Base64 is not encryption. It provides no security. anyone can decode it in seconds. Encoded data is approximately 33% larger than the original because each 3 bytes of binary becomes 4 characters of Base64.

Common Use Cases

Base64 encoding is ubiquitous in web development. JWTs (JSON Web Tokens) use Base64url encoding for their header and payload sections. Basic HTTP authentication encodes credentials as username:password in Base64. Email attachments are Base64-encoded in the MIME standard. Inline images in HTML (src="data:image/png;base64,...") use Base64 to avoid extra HTTP requests. API payloads that need to include binary data (file uploads, cryptographic keys, certificates) encode them as Base64 strings to maintain JSON compatibility.

URL-Safe Base64

Standard Base64 uses + and / characters, which have special meaning in URLs and must be percent-encoded if used in query parameters. URL-safe Base64 (Base64url) replaces + with - and / with _, making it safe for URL parameters and filename use without escaping. JWTs use Base64url. When passing Base64-encoded data in query strings, always use Base64url encoding or percent-encode the standard Base64 output.

Base64 vs Encryption

A common mistake is treating Base64 encoding as a security measure. It isn't. Base64 is reversible by anyone. there's no key, no secret, no computational cost to decode. If you need to protect data, use actual encryption (AES-256, ChaCha20) with a secret key. If you need to verify integrity, use a hash (SHA-256) or HMAC. Use Base64 only for what it's designed for: safely representing binary data as text for transmission or storage in text-only contexts.

Sources & Further Reading

Frequently Asked Questions

Is Base64 encoding the same as encryption?
No. Base64 is a reversible encoding scheme with no secret key — anyone can decode it instantly. It is designed to safely represent binary data as ASCII text for transmission, not to protect it. If you need to protect data, use actual encryption such as AES-256 with a secret key.
Why does Base64 output end with = or == signs?
Base64 encodes every 3 bytes of input into 4 characters. When the input length is not divisible by 3, padding characters (=) are added to make the output length a multiple of 4. One = means one byte of padding was needed; == means two bytes were needed.
What is the difference between standard Base64 and Base64url?
Standard Base64 uses + and / characters, which have special meaning in URLs and must be percent-encoded in query strings. Base64url replaces + with - and / with _, making the output safe to use directly in URLs, filenames, and HTTP headers without escaping. JWTs use Base64url encoding.
How much larger is Base64 output than the original data?
Base64 output is approximately 33% larger than the original binary input because each 3 bytes of input becomes 4 characters of output. A 1 MB file encoded as Base64 becomes roughly 1.37 MB. This overhead matters when embedding large images as data URIs in HTML or CSS.

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