Base64 and URL encoding (percent encoding) both transform strings into a safer form for transmission — but they are not interchangeable. Picking the wrong one breaks query strings, bloates URLs, or produces data that cannot be decoded on the other end. This guide explains what each encoding does, when to use it, and how they differ in practice.
Try both with our Base64 Encoder and URL Encoder — both run locally in your browser.
What is Base64 encoding?
Base64 converts binary data (or text) into a string using 64 ASCII characters: A–Z, a–z, 0–9, plus+ and /, with = padding. It is designed to carry binary data through text-only channels like JSON, email (MIME), and XML.
Input: Hello Base64: SGVsbG8=
Base64 output is roughly 33% larger than the original. It is reversible — decoding recovers the exact original bytes.
What is URL encoding?
URL encoding (percent encoding) replaces characters that are reserved or unsafe in URLs with a percent sign followed by two hexadecimal digits. Spaces become %20, ampersands become %26, and non-ASCII characters become multi-byte percent sequences.
Input: cats & dogs Encoded: cats%20%26%20dogs Full URL: https://example.com/search?q=cats%20%26%20dogs
URL encoding keeps strings human-readable for the most part. It is scoped to making data safe inside URLs and form submissions — not for carrying arbitrary binary.
Key differences at a glance
- Purpose: Base64 carries binary through text; URL encoding makes strings safe inside URLs.
- Character set: Base64 uses A–Z, a–z, 0–9, +, /; URL encoding uses percent codes like %20.
- Size change: Base64 grows ~33%; URL encoding grows only for special characters.
- Where it appears: Base64 in JWTs, data URLs, email attachments; URL encoding in query strings and form data.
When to use Base64
- Embedding small images in CSS or HTML via
data:image/png;base64,...data URLs. - Encoding binary attachments in JSON API payloads.
- Representing binary hashes or ciphertext as text.
- JWT payloads and headers (which use Base64URL — a URL-safe variant without + and /).
Decode any JWT using our JWT Decoder.
When to use URL encoding
- Building query strings:
?search=hello%20world - Encoding form field values in GET or POST requests.
- Passing user input into redirect URLs safely.
- Encoding path segments that contain spaces or special characters.
In JavaScript, use encodeURIComponent() for individual parameter values and encodeURI() for full URLs where you want to preserve structural characters like / and ?.
Common mistakes
Using Base64 in query parameters
Base64 strings contain +, /, and = — characters with special meaning in URLs. If you must put Base64 in a URL, use Base64URL encoding (which replaces + with - and / with _) and still URL-encode the result if needed.
URL-encoding binary data
Percent-encoding every byte of a binary file produces an enormous, inefficient string. That is what Base64 is for.
Double encoding
Encoding a string twice — for example, URL-encoding an already-encoded value — produces %2520 instead of %20. Always know whether your framework encodes automatically before adding your own encoding layer.
Worked example: same string, two encodings
Original: price=$100 & up URL encoded: price%3D%24100%20%26%20up Base64: cHJpY2U9JDEwMCAmIHVw JWT-style Base64URL (no + / =): cHJpY2U9JDEwMCAmIHVw (same here, but +/= would differ for binary)
For a query parameter value, URL encoding is correct. Base64 would work but adds unnecessary overhead and introduces URL-unsafe characters.
Frequently asked questions
Is Base64 encryption?
No. Base64 is encoding, not encryption. Anyone can decode it instantly. Never treat Base64 as a security measure.
What is Base64URL?
Base64URL replaces + with - and / with _, and often omits padding. JWTs use this variant so tokens can appear in URLs and headers without extra escaping.
Should I encode the entire URL or just the parameter?
Encode only the dynamic parts — parameter values and path segments with user input. Encoding the entire URL including https:// and slashes will break it.