Chrome Extension

Gnomad Capture

Full-page screen capture, scroll stitching, and selective redaction browser tool exporting to PNG or paginated PDF.

Client: David the Gnomad Inc.
  • JavaScript
  • Chrome Extension MV3
  • Canvas API
  • jsPDF
  • chrome-extension
  • screenshots
  • canvas
  • productivity

Capture, Stitch, and Redact

Gnomad Capture is a privacy-first browser extension that captures and edits full webpages without sending screenshots to external servers. It stitches screenshots locally, hides repeating sticky menus, and lets you crop or redact sensitive data (like keys or emails) before saving to PNG or PDF.

Technical Highlights

1. Programmatic Scrolling & Stitching

The background script uses Chrome’s tab capture APIs to record viewports as it programmatically scrolls the webpage. It then stitches these chunks together onto an HTML5 Canvas, correctly adjusting for variable scroll containers and screen ratios.

2. Sticky Header Suppression

To prevent headers and navigation menus from repeating in every stitched slice, the extension injects temporary styles to hide fixed or sticky DOM elements during the capture sequence, restoring them immediately after.

3. Client-Side Redaction & Export

The editor interface includes a Canvas wrapper that lets users click and drag to place black redaction boxes over sensitive text. Captured pages can be copied directly to the clipboard or compiled into multi-page, formatted PDFs using jsPDF.