macOS Preview added a redaction feature in recent versions. It works, mostly. On older macOS versions, redaction is either missing or unreliable — and 'highlight in black' isn't redaction.
For Macs where Preview's redact is questionable, Flint is the cleaner option.
Preview's redaction state
macOS Monterey and later include a Redact tool. It does real redaction — stripping content under the black bar. macOS Big Sur and earlier don't have it. If you're on Big Sur or earlier, draw-on-top tools (rectangle annotation) are NOT redaction.
Flint as the macOS-version-independent option
Open redact PDF in Safari, Chrome, or any browser. Works the same regardless of macOS version. Drop your PDF, mark regions, apply redaction, save. Same flow as Preview's modern Redact, except it doesn't depend on which macOS you're running.
Verify on Mac
Open the redacted file in Preview, try to select text within redacted areas. If selection is empty, redaction is real. If text comes out, redaction wasn't applied properly — repeat in Flint and verify again.
Combine with other Mac PDF flows
Redact in Flint, then use Preview for signing if you prefer. Or do everything in Flint: sign, merge, compress, all in the browser, no app install required.
FAQ
Does Preview's redact work the same as Flint's?
Functionally similar on Monterey+. Both strip underlying content and overlay a black mark.
What if I only have Preview from an older macOS?
Use Flint — Preview's older versions don't have proper redaction.
Is my file uploaded?
No. Flint runs in your browser. The file stays on your Mac.
Can I use Shortcuts to automate Flint?
Not directly — Flint is a web tool. For scripted Mac workflows, command-line PDF tools (qpdf, pdftk) are more automation-friendly.
Version-independent, browser-based. Redact on Mac.