JSON Feed Validator
Validate JSON Feed (v1.1) structure, required fields, and display feed summary.
How it works
- 1Paste or type your text in the input field
- 2Click "Validate" — processing happens in your browser
- 3Copy the result or download as a text file
What to do next
About JSON Feed Validator
JSON Feed Validator is the kind of utility you bookmark and reach for when you need it. Validate JSON Feed (v1.1) structure, required fields, and display feed summary. It loads quickly, works on any modern browser, and produces a result you can download or copy in a single click.
The right moment to reach for JSON Feed Validator 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.
JSON Feed Validator is a static page plus a client-side engine. The browser does the work; there is no separate backend in the loop for the actual processing. That architecture is why the tool starts immediately, why it does not depend on the load on a remote service, and why running multiple jobs in a row does not slow it down.
Behind the controls you see, standard browser APIs is doing the actual developer utility. Formats are detected on load and the engine produces a deterministic output for any given input + options combination — useful when you need to re-run a job and expect identical results.
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.
Anyone who works with developer utility on a casual basis — site reliability engineers triaging logs, devops engineers crafting one-liners, backend developers inspecting requests — finds JSON Feed Validator a quick way to get the result. The page loads in under a second, the controls are visible from a single screen, and the result downloads or copies in one click.
The download is delivered as a clearly named file the moment processing completes — no email link, no "your result will be ready in 5 minutes" queue, no expiry timer. The file is generated in your browser and saved by your browser's normal download flow.
Workflow tip: JSON Feed Validator pairs well with RSS Feed Validator and Atom Feed Validator. Other adjacent tools you may find useful are XML Sitemap Parser and robots.txt Tester. Because every tool is a separate page, you can mix and match the steps that match your job. Bookmark the ones you reach for the most.
JSON Feed Validator is honest about scope: it handles a single, well-defined developer utility step. Specialist edge-case work — uncommon formats, very large inputs, or pipelines that need scripting — is what dedicated desktop apps are for. This page handles the common case quickly.
Some context on why JSON Feed Validator 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. JSON Feed Validator is built on top of that capability, which is why a single page can host the full pipeline.
If you also use a command-line tool for json feed validator, JSON Feed Validator is a convenient alternative for the times you are on a different machine or helping someone who is not comfortable in a terminal. The output is a standard file in the format documented above.
Pro tip: JSON Feed Validator works just as well in a private/incognito window as in a normal one, which is occasionally useful when you want zero browser-history footprint of the job. Another tip: if the tool ever feels slow, it is almost always because the browser tab is competing for CPU with another tab — pausing or closing the heavy ones gives the engine room to work.
If JSON Feed Validator 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.
JSON Feed Validator is intentionally narrow in scope so the common case is fast and the result is predictable. If you ever need a variation it does not cover, browse the rest of the catalog — there is a good chance an adjacent tool already exists, and switching between tools is just a matter of opening another tab.
How it works
- 1Open the JSON Feed Validator workspace above. The interface is a single page, so there is nothing to navigate.
- 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.
- 5Save the output when it is ready.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Generate a quick fixture without leaving the browser using JSON Feed Validator.
- Generate boilerplate from a single specification line.
- Compare two API responses to spot a regression.
- Hash a string for a quick reproducibility check.
- Convert between data formats while wiring up an integration.
- Encode binary content for transport in a JSON body.
- Pretty-print a minified blob during incident triage.
- Format a noisy log line into something a teammate can read.
- Inspect a regex against a test string before committing it.
- Inspect a payload during local development without writing a script.
FAQ
What version?
Validates JSON Feed version 1 and 1.1 as defined at jsonfeed.org.
Required fields?
version, title, and items array. Each item needs a unique id.
JSON Feed vs RSS?
JSON Feed uses JSON instead of XML — simpler to parse and generate.
What is checked?
Required fields, URL validity, item structure, and content types.
Hubs and authors?
Optional fields like hubs, authors, and attachments are validated if present.
Private?
Yes — validation runs locally.
Does JSON Feed Validator upload my file to a server?
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.
Why use JSON Feed Validator instead of a paid online tool?
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. JSON Feed Validator 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.
Can I call JSON Feed Validator from a script?
JSON Feed Validator is a browser-only tool by design and does not expose a hosted API. The reason is the same as the privacy story: there is no Favtoo backend doing the work, so there is no service to call. If you need to script the same transformation, the underlying engine (standard browser APIs) is open-source and can be used directly from your own code.
Does JSON Feed Validator ask for any browser permissions?
JSON Feed Validator only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.
Does JSON Feed Validator work in Safari, Firefox, Chrome and Edge?
JSON Feed Validator 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.
Can I self-host JSON Feed Validator for my team?
JSON Feed Validator 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.
What should I do if JSON Feed Validator 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.