// BROWSER EXTENSION
File slicing in the browser
When you attach a file to a supported AI chat site, Omna steps in between your browser and the upload. It captures the file before the site sees it, sends it to the Omna Mac app for slicing, and swaps in a lean, masked copy — all in the background. From your side, you just clicked attach and picked a file.
How interception works
- Click the attachment button on a supported site (claude.ai, chatgpt.com, gemini.google.com, perplexity.ai, or chat.deepseek.com) and pick your CSV, Excel, PDF, or Word file as usual.
- Omna captures the file at the browser level before it's submitted — the site hasn't seen it yet.
- The extension hands it to the Mac app over Chrome's Native Messaging — a secure, local-only channel that never touches the network.
- The Mac app slices the file using your most recently typed question, keeps only the relevant rows, and masks any PII in them.
- The sliced copy is swapped in — the AI site receives the smaller version and processes it as if it were your original.
- A result banner appears above the composer showing rows sent, token reduction, estimated savings, and any PII fields masked.
Slice mode vs. Advisory mode
Switch between these in the popup (gear icon → File Handling). The change takes effect immediately.
Slice mode (default)
Omna intercepts the file, keeps only the rows relevant to your question, masks PII, and swaps in the slice. The AI sees the slice; the original never leaves your machine. Best for most users — maximum token and cost reduction.
Advisory mode
Omna doesn't slice. The original passes through unchanged, but Omna runs its local PII scanner and warns you before you send if it finds sensitive content. Use this when you deliberately need to send the full file.
If the Mac app isn't running
The result banner
| Banner | Colour | What it means |
|---|---|---|
| Token Tax killed | Green | File fit the context window; Omna sent a small, relevant slice — real savings |
| Token Tax crushed | Green | File was too large for the window; Omna's slice fits cleanly under the limit |
| Token Tax redirected | Amber | Even the slice fills the window — same cost, but the right rows are in it |
| All rows matched | Blue | Your question matched every row, so nothing was filtered — shown for transparency |
The banner also shows rows sent vs. total, token-reduction percentage, estimated dollar savings, and a chip for any PII fields masked.