Secure In-Browser PDF Compressor

How In-Browser Cryptographic PDF Compression Works

Online government recruitment portals (UPSC, SSC, State Civil Services), global visa systems (US DS-160, Schengen Visa, Canada Express Entry), and academic portals enforce rigorous PDF file limits—often rejecting any file that exceeds 100 KB, 200 KB, or 500 KB. Simultaneously, uploading sensitive documents like bank statements, passport scans, and tax returns to unknown cloud servers introduces severe identity theft risks.

1. Zero-Knowledge Local Memory Execution

Unlike conventional web compressors that send your documents across unencrypted networks to remote processing queues, Sys-Metrics executes 100% of the PDF workflow inside your local browser memory. The engine relies on WebAssembly compilation of Mozilla's PDF.js to parse and decompress object streams locally.

2. Cryptographic SHA-256 Digest Verification

Every time you process a file, our tool leverages the native W3C Web Crypto API (window.crypto.subtle.digest) to compute a cryptographically deterministic 256-bit hash of both the source document and the optimized output. This provides mathematical certainty of data integrity and proves the file was never touched by external servers.

3. Adaptive Triad-Budgeting Algorithm

To reduce multi-page PDFs to exact portal specifications, the engine budgets the target file size across every individual page:

• Page Weight Allocation: Subtracts the structural PDF dictionary overhead ($\approx 1.5\text{ KB}$) and divides the remaining byte budget equally among pages.
• Dynamic JPEG Re-quantization: Runs binary search quantization over the DCT compression coefficients for embedded raster streams until the page fits strictly under its allocated quota.
• Standards Compliance (ISO 32000-1): Reassembles pages into clean, linear cross-reference table structures compatible with all PDF viewers including Adobe Acrobat, Apple Preview, and mobile browsers.

4. Standard Online Submission Limits Table