ToolKitSphereFree Online Base64URL Encoder & Decoder
URL-safe Base64 encoding and decoding without padding or special URL characters.
43 characters · 9 words · 43 bytes (UTF-8)
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This Base64URL tool encodes text into URL-safe Base64 format and decodes it back, running entirely in your browser. Standard Base64 uses '+' and '/' characters that break URLs and file names, so Base64URL swaps them for '-' and '_' and typically drops the trailing '=' padding — this is exactly the variant used inside every JWT header and payload segment, as well as in URL query parameters and file-safe identifiers. Developers debugging JWT tokens, building URL shorteners, or encoding data for query strings will find this converter does exactly what's needed without any format surprises. All conversion logic runs as JavaScript locally on your device — no text is ever uploaded to a server, which is important if you're decoding a JWT payload that might contain sensitive claims. There's no signup and no rate limiting; results appear as you type. If you're working with full JWT tokens, this platform's JWT decoder handles the header/payload/signature breakdown for you automatically. Scroll down to encode or decode Base64URL text now.
Features
- URL-safe Base64 encoding using '-' and '_' instead of '+' and '/'
- Optional padding removal to match strict Base64URL variants
- Instant client-side conversion, no server call
- One-click copy to clipboard
- Correctly decodes both padded and unpadded input
- Supports arbitrary-length UTF-8 text
- Matches the exact encoding used inside JWT segments
- Works fully offline once the page loads
Why use this base64url encode / decode?
- Instant conversion with no delay
- Fully private, browser-only processing of your data
- Standards-accurate output matching JWT and URL encoding specs
- Simple two-way converter, easy for any skill level
- Free to use with no signup or limits
Frequently asked questions
What's the difference between Base64 and Base64URL?
Base64URL replaces the '+' and '/' characters used in standard Base64 with '-' and '_' respectively, and typically omits '=' padding, making the output safe to embed directly in URLs and filenames.
Why do JWTs use Base64URL instead of Base64?
JWTs are often transmitted in URLs and HTTP headers, where standard Base64's '+', '/', and '=' characters would need extra escaping — Base64URL avoids that problem entirely.
Is Base64URL encoding secure?
No, it's just an encoding, not encryption — anyone can decode Base64URL data instantly, so never use it to hide sensitive information.
Does Base64URL use padding?
It can, but most implementations, including JWTs, omit the '=' padding characters since the decoder can infer the correct length.
Can I decode a JWT payload with this tool?
Yes, pasting the middle segment of a JWT (between the dots) will decode its Base64URL-encoded JSON payload, though the dedicated JWT decoder tool provides a full structured breakdown.
Does Base64URL change the size of the data?
Yes, like standard Base64, it increases size by roughly 33% since 3 bytes of input become 4 output characters.
Is Base64URL reversible?
Yes, it's a fully reversible encoding — decoding always recovers the exact original bytes.
From the blog
What Is Base64 and Why Do Developers Use It?
What is Base64? A plain-English explanation of the 64-character alphabet, the 3-bytes-to-4-characters math, padding, the 33% size cost, and where it is used.
How to URL Encode a String (and When You Must)
URL encoding explained: which characters need percent-encoding, why a space is %20 in a path but + in a query string, and how to avoid double-encoding bugs.
Base64 Is Not Encryption: Correcting a Dangerous Myth
Is Base64 encryption? No. Here is why encoding provides zero confidentiality, how anyone decodes it instantly, and what to use instead when data must stay secret.