Most "secure" online converters are server-based with SSL on the connection. SSL protects data in transit, but the data still arrives at the vendor's server, where it is processed, possibly logged, and possibly retained per the vendor's retention policy. The vendor employees may have access. The vendor's subprocessors may have access. The vendor's breach surface includes your data. SSL is necessary but not sufficient for genuine privacy.
FixTools is architected differently. The JavaScript that performs the conversion runs in your browser, not on a server. Your JSON is parsed, flattened, and serialised in client-side code. The CSV download is generated as an in-memory blob and saved locally via the browser's file API. At no point does any byte of your input or output touch the network. The only network traffic associated with the page is the initial page load (HTML, CSS, JavaScript assets) and any third-party advertising or analytics calls, which do not carry your data.
This architecture is verifiable end-to-end. Open Chrome DevTools or Firefox DevTools, switch to the Network tab, clear the list, and paste your JSON into the converter. Watch the Network tab as you click Convert and Download. You will see no outbound requests with file content. The only requests are static asset reloads and any ad calls, both of which are visible and audit-friendly. Many security teams require this kind of verifiable privacy for any tool that touches PII; FixTools is designed to pass that bar.
For absolute compliance certainty, run the tool in an offline browser tab. Load the page once with network access, then disable Wi-Fi or disconnect Ethernet. Refresh the tab; the page loads from browser cache. Convert your JSON; the conversion completes locally. Without a network connection, there is no possibility of data egress regardless of what the code does. This is genuinely useful for compliance teams that want to document the privacy posture of a third-party tool.