Does it auto-encode spaces and special characters?

Yes — path segments use percent-encoding (space → %20). Query values use form-style encoding (space → +, although %20 also works). Hash fragment is encoded per the URL spec. Idempotent: re-encoding an already-encoded string doesn't double-encode.

What if I need a port number?

Optional field. The default ports (80 for http, 443 for https) are omitted from the output even if you set them — those are implicit. Non-default ports (8080, 3000) are included.

How is this different from query-string-builder?

URL Builder assembles the full URL including protocol and host. Query String Builder just builds the ?key=value portion — useful when you have a fixed URL and only need to append params.

rfc 3986 · components · live · local

Build a URL from its parts

Q: Is anything sent to a server?

No — pure string assembly in your browser.

Assemble protocol, userinfo, host, port, path, query and fragment with proper encoding. All assembly runs in your browser.

URL Builder

Length

52 B

52 chars

Params

query keys

Status

valid

rfc 3986

Protocol

https

scheme

input · components

Host

Port

Path

User

Password

Fragment (#)

Query parameters

output · url

https://api.example.com/v1/users/42?fields=id%2Cname

Quick Start

How to assemble a URL

Each field maps to an RFC 3986 component. The output is encoded automatically.

01
Pick a scheme
https is the safe default. Use ws/wss for WebSocket endpoints.
Lookups reference the IANA registries (MIME, HTTP status, TLDs) bundled at build time — no live network calls, no rate limits, no leaked queries.
schemeIANAregistryofflinelive
scheme · queryhttps · IANA
```
https://
```
loaded · IANA bundlespec · ready
02
Set host + path
Host can include a port. Path is auto-prefixed with /.
Builders emit canonical syntax per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs) so the output passes spec-compliant parsers.
hostRFC 9110canonicalspec-compliantlive
host · optionspath · live
```
api.example.com/v1/users/42
```
options applied · livecanonical
03
Add query parameters
Each key/value is URL-encoded automatically.
Validation flags common pitfalls — uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8 — before they bite production.
queryvalidationlintpitfallslive
q · looked upencoded · ready
```
?fields=id%2Cname
```
result · livevalidated
04
Copy your URL
Validate via new URL() in the background. Then ship it.
Copy writes the snippet directly into your clipboard; downloads emit the right extension and MIME so curl/httpie pick them up correctly.
copyclipboardMIME-correctblobcurl-ready
ok · copiedready · done
```
Copied URL
```
shipped · ready to shipsuccess

Pro tips

Web-spec details that bite later

Idempotency saves retries

POST/PUT/DELETE should be safely retried. Use idempotency keys and return the same response on duplicate requests.

Match RFC 9110 status codes

Don’t invent codes. 422 for validation errors, 409 for conflicts, 429 for rate limits. Standard codes work with off-the-shelf clients.

Set <code>Cache-Control</code> deliberately

Default browser caching is conservative. Use max-age + stale-while-revalidate for hot endpoints.

Validate Open Graph in dev

OG tags break silently. Use a previewer like OG Generator + Facebook’s debugger before launch.

CORS is a server concern

The browser sends the preflight; the server decides. Wildcard origins disable credentials — be explicit.

MIME drives behaviour

Servers must send the right Content-Type. Browsers sniff but the spec says they shouldn’t — be explicit to avoid surprises.

Use Cases

When to build a URL by hand

API testing, integrations, docs.

API testing

Assemble URLs for curl/Postman without typing escapes. Bundled from IANA registries at build time — no live network call, no rate limit, no leaked queries. The MIME, TLD, and status-code tables are baked in so the tool works offline once loaded.

spec-compliant

Integration setup

Build webhook callback URLs precisely. Output is canonical per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs), so spec-compliant parsers accept it as-is. Cross-browser and cross-library behaviour stays consistent.

offline

Docs writing

Show readers exactly what a request URL looks like. Pairs with the curl-to-fetch converter for end-to-end test stubs — copy the curl from DevTools, paste, get an idiomatic fetch() body. Drop into Playwright/Vitest fixtures without manual translation.

IANA-backed

URL templates

Validate generated URLs before saving them. Catches common pitfalls (uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8) before they bite production. Validation flags rather than auto-corrects so you stay in control.

RFC-aligned

OAuth flows

Construct authorize URLs with all the right params. Validation runs as you type — copy only when the output is shaped correctly. The output drops directly into nginx, Apache, or CDN configs without re-formatting or re-quoting.

production-grade

Multi-region

Swap host quickly to test against different regions. Same input plus same options always produces identical canonical output, so the tool is safe to embed in CI scripts that diff against expected configs.

curl-ready

FAQ

Frequently asked questions

Are special characters encoded?

Yes — userinfo, query keys and values are URL-encoded via encodeURIComponent / URLSearchParams.

What about IDN hosts?

Type Punycode (xn--…) directly. We don't IDN-encode for you.

Validation?

We construct the URL with new URL() — invalid combinations show as an error in the output panel.

Why does HTTPS default to port 443?

Omit the port for default scheme ports. We don't add :443 implicitly.

Is anything sent to a server?

No. The URL is built locally in your browser.

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