Question 1

How does the PDF comparison engine work in PDFBlack?

Accepted Answer

PDFBlack runs an enterprise v4.0 engine based on the linear-space Myers Diff algorithm with common prefix and suffix pruning. It extracts exact viewport coordinates and typography for each word, detecting deleted, added, or relocated text between Base Document (A) and Modified Document (B) in milliseconds.

Question 2

Why is the tool strictly limited to comparing two files (Doc A vs Doc B)?

Accepted Answer

In legal, corporate, and audit compliance, rigorous document comparison is inherently binary: a baseline master document (Document A) against a revised draft (Document B). Restricting the workflow to strictly two files ensures unambiguous diff tracking, accurate similarity percentages, and certified audit reports.

Question 3

What is the Interactive Curtain Slider and how do I use it?

Accepted Answer

The Curtain Slider is an interactive split overlay that aligns pages from Document A and Document B. Dragging the divider line left and right allows you to immediately detect subtle signature shifts, modified logos, font kerning changes, or paragraph relocations that standard text comparators miss.

Question 4

Is it safe to compare confidential contracts or legal files on PDFBlack?

Accepted Answer

100% secure. PDFBlack processes both PDF files entirely client-side within your browser via dedicated Web Workers. No page, text, or image is ever uploaded to remote servers or stored in the cloud. Your data resides solely in local RAM.

Question 5

What structural changes does the engine detect besides text?

Accepted Answer

The engine audits page count deltas, dimensions and margin shifts (e.g. A4 Portrait to Letter or Landscape), added or removed font families, embedded graphic resource counts, and document metadata (Author, Title, Producer, Creation date).

Question 6

How does PDFBlack ensure the forensic validity of the exported reports?

Accepted Answer

Both executive PDF reports and TXT/JSON audits feature independent SHA-256 cryptographic hashes calculated directly over the binary bytes of both PDF documents via native Web Crypto API, providing verifiable proof of integrity.

Control & Change Auditing in PDF Documents

High-Efficiency Myers Diff

SHA-256 Cryptographic Audit

Curtain Slider & Heatmap

Zero-Server Total Privacy

Frequently Asked Questions