“This JSON stays in your browser” is a claim readers should be able to check. Chrome DevTools’ Network panel can show requests made while you use a particular feature, letting you inspect whether that run appears to send your JSON. It cannot prove that every feature, version, or future build will never transmit data.
How to check whether a JSON tool sends your input
- Open the relevant feature in Chrome. Open DevTools, select the Network panel, and do so before entering test data. Chrome records network activity while DevTools is open. See Chrome DevTools: Network panel.
- Use synthetic JSON. Enter harmless sample data, then trigger the specific operation you want to check, such as formatting or validation. Do not use credentials or production data as test material.
- Inspect requests and their details. Review the Requests table and relevant request details or payloads. A request count alone cannot tell you whether the input was sent: sites make requests to load pages, scripts, fonts, analytics, and other resources. The question is whether a request associated with the operation carries your test JSON.
- Repeat for each feature that handles input. Checking formatting does not show what a separate conversion, schema, or upload feature does.
- Record the limits of the observation. A Network-panel capture describes the session you observed, under the conditions in which you ran it. Chrome documents that responses can come from the local cache or a service worker, which can affect what appears in the panel. See Chrome DevTools: Network panel reference.
If you report a test publicly, include the browser and version, the feature exercised, the date or site version, whether cache was disabled, which requests you reviewed, and what you observed. Without those details, readers cannot tell the scope of the check.
What a clean Network-panel check does—and does not—show
If you exercise a feature and do not see a request carrying the synthetic input, that is evidence about that feature in that browser session. It is not proof that no other feature sends data, that the app’s code and dependencies cannot transmit it under other conditions, or that a later version will behave the same way. Those broader claims require evidence beyond one session’s request log.
Likewise, seeing requests does not by itself mean the JSON was uploaded. Inspect what each relevant request contains and when it occurs. Page resources or visit analytics are different from a request that carries the JSON being processed.
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Local JSON processing is not the same as no network activity
A tool can process JSON in the browser while its website still makes ordinary hosting, analytics, or advertising requests. Those are separate privacy questions: whether the input content leaves the browser, and whether the site collects other information about a visit.
For example, jsonfmt.dev’s policy says its core web application performs JSON operations locally and that it does not make requests carrying JSON content. The policy also covers separately named offerings, including an API, extension, CLI, and MCP server, so its claim should not automatically be applied to every offering. This is the vendor’s statement, not an independent audit: jsonfmt.dev privacy policy.
A separate formatter’s policy claims client-side JSON processing while also describing Google Analytics and AdSense collection of aggregate visit data and cookies. That illustrates why “my JSON is not uploaded” should not be rewritten as “the site makes no third-party requests” or “the site collects no visit data”: JSON Formatter privacy policy.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the privacy wording should promise
Changing “trust me” to “verify it in DevTools” makes a privacy statement more useful only if it is precise about what readers can verify. An honest version is: “Use Chrome DevTools’ Network panel to inspect whether this feature sends your input during your session.” If you have separately documented a test, state the browser, feature, date, and observed requests; do not present a reader’s possible check as a test you already performed.
The title’s tool is not identified here, and no independent capture or source audit establishes how it behaves. A vendor policy can explain what its publisher claims, but it is not independent confirmation. Keep the invitation to inspect behavior distinct from a guarantee about all data, features, or future versions.
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