What local processing means
Textareas, FileReader, ArrayBuffer, Canvas, Web Crypto, and other browser APIs can process data without sending the selected content to an application server. The browser still downloads the page code, styles, and scripts from the website.
A privacy claim should describe the specific workflow rather than imply the browser is offline. Network requests for fonts, analytics, ads, or other resources may still occur unless the site avoids them.
How different tools work
Text tools use pattern matching and parsing. Image tools can decode pixels into a canvas and export a newly rendered image. Hash tools pass file bytes to the Web Crypto API. Metadata viewers inspect known binary structures.
Each method has limits. Pattern matching cannot understand every context, and lightweight parsers cannot read every proprietary metadata format.
How to verify a local claim
Open developer tools, use the Network panel, select a test file containing fake data, run the tool, and confirm no request contains the file or pasted content. Repeat after updates or when third-party scripts change.
Use synthetic test data rather than real confidential information during verification.
What local processing does not guarantee
It does not guarantee complete anonymization, safe output, trustworthy code, malware protection, legal compliance, or protection after you paste the result into another service.
For high-risk data, use approved tools, access controls, retention rules, and professional review.
Final review checklist
- Tool workflow described precisely
- Network behavior tested with synthetic data
- Third-party scripts reviewed
- Output manually checked
- Organizational policy followed