CDN URL Builder
Build CDN URLs for popular services like jsDelivr, unpkg, cdnjs, and esm.sh with version pinning.
How it works
- 1Configure your options above
- 2Click "Generate" — processing happens in your browser
- 3Copy or download the result
What to do next
About CDN URL Builder
CDN URL Builder is a free, in-browser developer tool. Build CDN URLs for popular services like jsDelivr, unpkg, cdnjs, and esm.sh with version pinning. The page exposes a small surface — input, controls, output — so a first-time visitor can complete the job without reading documentation.
CDN URL Builder is implemented on top of standard browser APIs. Inputs are read from the file picker or drop zone, decoded in the browser, processed, and re-encoded into the output format. Files up to 0 MB are well within the comfort zone of any modern browser.
CDN 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.
If you fit any of these descriptions, CDN URL Builder should slot cleanly into your workflow: engineers debugging API payloads; backend developers inspecting requests; site reliability engineers triaging logs. The tool keeps the controls focused on what matters for each of these use cases.
CDN URL Builder works well as a bookmarked utility you reach for when you need it. The first visit shows you what the tool does; the second is when you realise it is a low-friction option for the task and worth keeping in your tab list.
The 0 MB ceiling on input size is the only fixed limit. Output files are produced in standard formats that every common viewer recognises, and the tool runs the same way regardless of how many times you have used it during the session.
If your task needs more than one step, chain CDN URL Builder with Cache-Control Generator, Content Security Policy Tester, and Web Manifest Generator. Each tool produces output that is a clean input to the next, so multi-step workflows are just a matter of opening the next tool in a new tab and continuing.
CDN URL Builder keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.
The output handed back by CDN 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 CDN 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. CDN URL Builder is built on top of that capability, which is why a single page can host the full pipeline.
As a single-page tool, CDN URL Builder stays focused on one developer utility step. Multi-step workflows are composed by chaining adjacent tools — each tool produces a standard file the next one can read directly, so a longer pipeline is just a sequence of short tab-and-tab visits.
A few practical tips that experienced users of CDN URL Builder pick up over time. First, keep your default browser updated — the engine relies on standard web APIs and newer browser versions are noticeably faster than ones from a few years ago. Second, close other heavy tabs before processing a large input; the engine shares CPU and memory with whatever else is open. Third, if you re-run the same kind of job often, your last-used settings are remembered for the rest of the tab session, so subsequent runs are essentially one click.
If CDN URL Builder appears to hang, the engine is almost certainly still working — large inputs simply take longer to process inside a browser than they would on a server with multi-core scheduling. For inputs near the 0 MB cap, give it up to a minute on a typical laptop before assuming something is stuck.
CDN URL Builder is one of many single-purpose tools in the catalog. Each is built around the same single-page model. Use this one, close the tab, and come back the next time you need the same job done. None of the tools require prior knowledge of the others — each page is self-contained.
How it works
- 1Reach the CDN URL Builder page in your browser to begin.
- 2Add your developer input by dropping it onto the page or browsing for it.
- 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.
- 6Repeat the process for additional inputs whenever you need to. The page stays loaded, so subsequent runs are quick.
Common use cases
- Format a noisy log line into something a teammate can read using CDN URL Builder.
- Hash a string for a quick reproducibility check.
- Compare two API responses to spot a regression.
- Inspect a regex against a test string before committing it.
- Generate boilerplate from a single specification line.
- Generate a quick fixture without leaving the browser.
- Decode a token to confirm its claims during a debugging session.
- Pretty-print a minified blob during incident triage.
- Encode binary content for transport in a JSON body.
FAQ
Which CDNs are supported?
jsDelivr, unpkg, cdnjs, esm.sh, and Skypack — the most popular JS CDN providers.
Can I pin a version?
Yes — specify exact version, semver range, or "latest" for the newest release.
File selection?
Choose between main/module entry point, or specify a custom file path.
Minified versions?
Most CDNs auto-serve minified versions. The tool appends .min.js when available.
SRI hash?
Subresource Integrity hashes are recommended but require a network lookup (not generated here).
Private?
Yes — URL construction runs locally.
What does CDN URL Builder do that command-line tools do not?
Desktop apps usually have more advanced features but require installation, maintenance and (often) a licence. Paid online tools are convenient but route your file through their servers and gate downloads behind accounts. CDN URL Builder sits in between: free, instant, and private, but intentionally narrow in scope. For one-off jobs and the common developer utility operations, it is usually the lowest-friction choice; for highly specialised work, a dedicated app is still the right answer.
Will CDN URL Builder keep working if my Wi-Fi drops mid-task?
Once the page is loaded, CDN URL Builder can complete jobs without an active internet connection — the engine is bundled with the page, so there is no per-job network call. The initial page load does require a connection (to fetch the static assets), but after that you can disconnect entirely and the tool will still work. This is a side-effect of the local-first architecture, not a deliberate "offline mode" feature.
What should I do if CDN URL Builder fails on my file?
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.
Can I use CDN URL Builder on documents that contain personal data?
Your file is processed inside your browser by standard browser APIs. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
How do I know I am using the latest version of CDN URL Builder?
CDN URL Builder is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Can I use CDN 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.
Do I need a specific browser to use CDN URL Builder?
CDN URL Builder works in any modern browser released in the last few years — Chrome, Edge, Firefox, Safari, Brave, Arc and the major Chromium derivatives are all supported. The underlying engine relies on widely-supported web APIs, so there is nothing exotic to install. If you are on a very old browser version and the tool fails to load, updating to the latest release of your preferred browser is the only fix needed.
Does Favtoo keep a copy of files I process with CDN URL Builder?
Favtoo keeps no copy of your file because Favtoo never receives your file. CDN 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.