URI Template Expander
Expand RFC 6570 URI Templates into final URLs in your browser. Query strings, path segments, fragments, lists, and explode modifiers with a live variable table.
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What is URI Template Expander?
The URI Template Expander is a free online implementation of RFC 6570, the IETF standard for parameterized URLs. Instead of hand-building query strings and worrying about encoding, you write one template, fill in a variable table, and copy the finished URL — with the exact same output a server-side expander would produce.
Key Benefits
- Guaranteed RFC 6570-compliant output, verified against the official test vectors.
- Instant feedback while you iterate on template design.
- Warnings for variables the template needs but you have not filled in.
- No sign-up, no upload, and no server — safe for private API work.
Common Use Cases
- •Prototyping REST API endpoint URLs before writing the client code.
- •Checking how OpenAPI path templates and Spring UriTemplate patterns expand.
- •Building documentation examples with concrete, correctly encoded URLs.
- •Generating test URLs for QA with different parameter combinations.
How to Use the URI Template Expander
- Enter your template: Paste or type an RFC 6570 template such as https://api.example.com/users/{id}{?fields} into the template field, or click an example chip to load a ready-made one.
- Fill in the variable table: Each row is one variable. Pick a type (string, list, or map), then enter its value. List values are comma-separated; map values are key=value pairs.
- Review the live output: The expanded URI updates instantly below. If the template references a variable with no row, a warning lists the missing names.
- Copy the result: Click Copy to put the final percent-encoded URL on your clipboard, ready for docs, tests, or your HTTP client.
Key Features
- Full RFC 6570 Level 1-4 support: all seven operators including reserved expansion and query continuation.
- Variable table with string, list, and map value types plus explode and prefix modifiers.
- Live expansion as you type, with undefined-variable warnings before you ship the template.
- Percent-encoding handled exactly per the RFC, verified against the official test vectors.
- One-click example templates for common REST API URL patterns.
- 100% client-side: works offline and keeps private API designs on your machine.
Frequently Asked Questions
What is a URI Template (RFC 6570)?
A URI Template is a standardized string with variables in curly braces, such as https://api.example.com/users/{id}{?fields}. RFC 6570 defines exactly how those variables are substituted and percent-encoded to produce the final URL. It is used by OpenAPI, Spring, and many HTTP clients.
What is the difference between {var} and {+var}?
Simple expansion {var} percent-encodes reserved characters like slashes. Reserved expansion {+var} keeps slashes, question marks, and colons as-is, which is why {+path} with /foo/bar yields /foo/bar instead of %2Ffoo%2Fbar.
What does the explode modifier (*) do?
The explode modifier expands a list or map into separate parts. For example, {?tags*} with tags=dev,web becomes ?tags=dev&tags=web instead of the comma-joined ?tags=dev,web — the format most APIs expect for repeated query parameters.
Does my data leave the browser?
No. The entire RFC 6570 engine runs as plain JavaScript in your browser. There is no server call, no upload, and the tool works offline, so internal API designs stay private.