PWA Manifest Validator
Validate a web app manifest JSON for PWA installability requirements and best practices.
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 PWA Manifest Validator
PWA Manifest Validator is shaped around how people actually use developer utility utilities online: open the page, drop in a file, get the result. Validate a web app manifest JSON for PWA installability requirements and best practices. The interface stays out of the way once the work begins so the engine can use the available CPU and memory for the actual transformation.
Common audiences for PWA Manifest Validator include frontend developers prepping fixtures and students learning new languages, but plenty of people land on the page through a one-off search and never come back — that is also fine. The tool is built to be useful even when you only ever need it once.
Most people land on PWA Manifest Validator via a search at the moment they actually need the tool. That shapes the design: the page is a single screen with the input on one side, the controls in the middle, and the result on the other, so a first-time visitor can complete the job without reading documentation.
The engine behind the page is standard browser APIs. It reads your file in-memory and writes the result back into the browser. For 0 MB and below the work usually completes in seconds; larger files mostly depend on how much spare RAM your device has.
The browser sandbox isolates the page's JavaScript from the rest of the system, the same way it isolates every other tab you have open. PWA Manifest Validator works inside that sandbox: it reads the file you give it, processes it with standard browser APIs, and writes the result back. Nothing leaves the page's memory unless you choose to download or copy it.
Even on its own, PWA Manifest Validator composes well with the rest of your toolkit. The output is a standard developer file that opens in any program that handles the format, so the result of one run can become the input to whatever step you use next.
The hard constraints are easy to remember. Maximum input: 0 MB. Multiple files per run: no — one input at a time, by design, to keep results predictable. The same controls apply on every run.
PWA Manifest Validator 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.
Once the engine finishes, the output is offered as an immediate download. There is no preview gate, no email-wall, and no "register to download" intermediary — the file is yours the moment it is ready.
PWA Manifest Validator is structured around the idea that a useful tool should be its own page. Open the page, do the work, close the tab — the page is the entire product. There is no onboarding flow because there is nothing to onboard into.
PWA Manifest Validator fits the gap where opening a desktop app feels heavy and writing a script feels overkill. The page handles the common developer utility task with sensible defaults so a single visit usually completes the job; for highly specialised work, a dedicated desktop application can offer more knobs to turn.
A few practical tips that experienced users of PWA Manifest Validator 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.
Common gotchas worth flagging: the supported formats are listed in the upload area. The 0 MB ceiling is per-file, not per-session; you can run as many separate jobs as you like, but a single oversized input will be rejected on load.
If PWA Manifest Validator solved your problem, sharing the page link with someone who has the same problem is the most useful thing you can do. The catalog grows mostly through word of mouth; visitors arriving through a recommendation tend to be the ones the tool serves best.
How it works
- 1Land on the PWA Manifest Validator page. The tool is ready to use the moment the page renders.
- 2Select the developer file you want to process — drag-and-drop and the file picker both work.
- 3Pick any non-default settings you need. Most users leave the defaults alone for the first run and only revisit if the result needs tuning.
- 4Trigger processing. standard browser APIs reads your input, applies the transformation, and writes the result back into the page.
- 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.
- 6Re-run with different settings as often as you want. Each run produces a fresh output and the original file on disk is never modified.
Common use cases
- Convert between data formats while wiring up an integration using PWA Manifest Validator.
- Format a noisy log line into something a teammate can read.
- Validate a config blob before pushing to staging.
- Inspect a regex against a test string before committing it.
- Hash a string for a quick reproducibility check.
- Inspect a payload during local development without writing a script.
- Decode a token to confirm its claims during a debugging session.
- Generate boilerplate from a single specification line.
- Compare two API responses to spot a regression.
- Encode binary content for transport in a JSON body.
FAQ
What is checked?
Required fields, icon sizes, display mode, start_url, theme_color, and background_color.
Installability?
Checks if the manifest meets Chrome, Edge, and Firefox PWA install criteria.
Icon requirements?
At least 192×192 and 512×512 PNG icons with correct type and sizes attributes.
Best practices?
Checks for short_name length, description, categories, and screenshots.
Maskable icons?
Warns if no maskable icon (purpose: "maskable") is declared for adaptive icon support.
Private?
Yes — validation runs locally.
Does PWA Manifest Validator require a browser extension or plug-in?
No installation is needed. PWA Manifest Validator runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use PWA Manifest Validator on any computer you have temporary access to without leaving anything installed on it.
Are there any usage limits on PWA Manifest Validator?
Inputs are capped at 0 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run PWA Manifest Validator as often as you need; every run produces a full-quality result.
Can I process multiple files at once with PWA Manifest Validator?
PWA Manifest Validator 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.
What input formats are supported by PWA Manifest Validator?
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.
Does PWA Manifest Validator work on a phone or tablet?
PWA Manifest Validator 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.
Does PWA Manifest Validator need an internet connection to run?
Once the page is loaded, PWA Manifest Validator 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.
Can I call PWA Manifest Validator from a script?
PWA Manifest 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.
Is PWA Manifest Validator really free?
PWA Manifest Validator 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.
Will I notice a difference in the output from PWA Manifest Validator?
PWA Manifest Validator 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.