URL Builder
Build URLs from components — set protocol, host, port, path, query parameters, and fragment with auto-encoding.
How it works
- 1Configure your options above
- 2Click "Generate" — processing happens in your browser
- 3Copy or download the result
What to do next
About URL Builder
URL Builder is an developer tool that runs in your browser. Build URLs from components — set protocol, host, port, path, query parameters, and fragment with auto-encoding. The page you are reading is the same workspace you will use to do the work: pick a file or paste your input, choose the options that matter to you, and the tool produces the result on your device.
Architecturally, URL Builder is a single-page client. The processing layer is standard browser APIs; the UI is a thin React shell on top. Inputs flow through the engine and the output is returned to the browser as a Blob you can save or copy. The 0 MB cap is the only hard limit and it exists to keep memory usage stable on every device.
URL Builder runs the entire transformation inside your browser. The file is read by JavaScript running in the page, processed in-memory by standard browser APIs, and written back as a download. The browser is the runtime; the page is the interface. You can confirm what the tool does by opening the developer-tools Network tab during a run — the only requests are for the page's own static assets.
The heaviest users of URL Builder tend to be site reliability engineers triaging logs, engineers debugging API payloads and backend developers inspecting requests. Each group brings slightly different expectations to the tool, but the same single-page architecture serves every one of them with the same response time.
The right moment to reach for URL Builder is when you have a focused developer utility job that fits inside a browser tab. Open the page, drop in the file or paste your input, choose the options that matter, and the tool returns the result.
Constraints worth knowing about: inputs are capped at 0 MB to keep memory usage in a sensible range, one input is processed per run, and the tool must be loaded over HTTPS for the in-browser engine to work. These are properties of the architecture.
Once you have used URL Builder, the natural next steps depend on what you are doing with the result. Common follow-ups include URL Parser, Query String Builder, and Sitemap XML Generator. These are surfaced on the page so you do not have to hunt the catalog manually.
URL Builder is built around steady iteration on a small set of options rather than feature creep. Every additional setting attracts a slightly different audience, but a long settings panel makes the common case slower for everyone. The current controls reflect what users of the tool actually use.
The output handed back by URL Builder is the output file. If you would prefer to keep the result in the browser instead of downloading it, you can copy it from the result panel and paste it directly into another tab — useful when the next tool in your workflow expects pasted text rather than a file.
Some context on why URL Builder exists in this form: modern File APIs, high-performance JavaScript engines, and well-maintained open-source libraries now make it possible to perform developer utility work entirely in the browser. URL Builder is built on top of that capability, which is why a single page can host the full pipeline.
URL Builder produces deterministic output: the same input plus the same options always produces the same result. That predictability matters when the result has to match an upstream specification or be reproducible later.
Useful patterns when working with URL Builder: keep the input file open in another tab so you can compare against the result; give the output file a descriptive name when saving so you can find it later (the default name is sensible but generic); and treat each run as independent — the tool has no concept of "history", which means you cannot accidentally pollute one job with leftovers from another.
When something goes wrong, the cause is usually one of three things: a malformed input, a browser that is out of memory, or a corporate proxy that is interfering with the page's static assets. The first two are easy to diagnose; the third typically requires asking your IT team to allow standard browser APIs to load.
Open the workspace above to start using URL Builder. The engine loads on the first interaction so the page itself stays light, and once the tool is warm it processes subsequent jobs quickly. The moment the page is interactive, the tool is ready to do real work on your file.
How it works
- 1Open the URL Builder workspace above. The interface is a single page, so there is nothing to navigate.
- 2Select the developer file you want to process — drag-and-drop and the file picker both work.
- 3Adjust the options to match what you need. Sensible defaults cover the most common case, so you can usually skip this step.
- 4Hit the run button. standard browser APIs does the work in your browser tab.
- 5Grab the output as soon as the run completes. You can also copy the result instead of downloading if the next tool in your workflow accepts pasted input.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Validate a config blob before pushing to staging using URL Builder.
- Pretty-print a minified blob during incident triage.
- Generate boilerplate from a single specification line.
- Hash a string for a quick reproducibility check.
- Decode a token to confirm its claims during a debugging session.
- Inspect a regex against a test string before committing it.
- Inspect a payload during local development without writing a script.
- Generate a quick fixture without leaving the browser.
- Compare two API responses to spot a regression.
FAQ
Are values URL-encoded?
Yes — query parameter keys and values are automatically URL-encoded to handle special characters like spaces and ampersands.
How do I add query parameters?
Enter key=value pairs, one per line. They will be joined with & and appended after ?.
Can I use custom ports?
Yes — leave the port field empty for default (80/443) or enter a custom port number.
Does path need a leading slash?
A leading slash is added automatically if you omit it.
What about the hash/fragment?
Enter the fragment name without the # symbol — it will be appended as #fragment.
Private?
Yes — URL built locally.
Is URL Builder really free?
URL Builder is free to use. The processing runs in your browser, which keeps the per-user cost low enough that the tool can be offered openly. The download is the same file the engine produced — you can use it for as many runs as you need.
Why did URL Builder reject my input?
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is in a supported format and that it is below 0 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
How accurate is URL Builder?
URL Builder is built on standard browser APIs, which is the same class of engine used by professional developer utility pipelines. For deterministic operations, the output is byte-identical to what an equivalent CLI run would produce; for operations involving a codec or a model, the result is well within the range of what comparable tools generate. If you have a specific reference output you need to match, run a small test job first to confirm the configuration produces what you expect.
Is URL Builder lossless?
URL Builder is built to preserve quality wherever the underlying developer format allows it. Operations that are mathematically lossless (e.g. structural transformations, lossless re-encoding) round-trip with no perceptible change. Operations that involve a lossy codec inevitably introduce small artefacts at the byte level, but the defaults aim at the sweet spot where output looks or sounds the same to a normal viewer or listener while still being meaningfully smaller or faster than the input.
Can I use URL Builder on iOS or Android?
URL Builder runs in any modern mobile browser — Safari, Chrome, Firefox and the in-app browsers in most messaging apps all support the underlying APIs. Performance depends on the device: a recent phone handles typical inputs nearly as fast as a laptop, while older devices may take a few seconds longer near the 0 MB ceiling. The interface lays out cleanly on small screens, so you do not need to pinch-zoom to see the controls.
Are jobs run with URL Builder stored anywhere?
Favtoo keeps no copy of your file because Favtoo never receives your file. URL Builder runs entirely in your browser, the input is held only in your tab's memory, and closing the tab discards it. There is no opt-in cloud history, no "recent jobs" panel synced to an account, and no server-side retention to configure — the architecture simply has nowhere for your file to be stored.
Can I process multiple files at once with URL Builder?
URL Builder processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
Can I use URL Builder with formats other than the defaults?
The accepted formats are listed in the upload area on the tool itself. If your input is in a format that is not directly supported, convert it first using one of Favtoo's converter tools — every Favtoo converter outputs a file that is a clean input to the next tool in the chain.
Can URL Builder run inside a corporate firewall?
URL Builder is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (standard browser APIs) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.