WebCopy will attempt to create local filenames based on the remote URL, with a numeric prefix if a file already exists.

Without deterministic filenames, multi-threaded crawls process URLs in an unpredictable order, potentially causing the same URLs to receive different numeric suffixes across runs. This makes comparing crawls difficult, breaks automated workflows that depend on consistent paths, and prevents reliable incremental updates. To address this, WebCopy can embed a CRC32 checksum of the remote URL in the filename, ensuring the same URL always generates the same local filename regardless of processing order.

Example file names:

Remote URLNon-deterministicDeterministic
/productsproducts.htmlproducts-6dd9dcef.html
/products?onlyinstock=1products-1.htmlproducts-9169ec94.html

Important

It is still possible for filenames to be non-deterministic if the full path name is longer than 260 characters as it will then get automatically truncated.

Use deterministic filenames

Important

This feature is automatically enabled for new WebCopy projects. It remains disabled when opening projects saved using older versions of WebCopy, although can be toggled on.

  1. From the Project Properties dialogue, select the Local Files category
  2. Check the Use deterministic file names option

See Also

Configuring the Crawler

Working with local files

Controlling the crawl

JavaScript

Security

Modifying URLs

Creating a site map

Advanced

Deprecated features

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Documentation version 1.10 (buildref #191.16188), last modified 2026-02-13. Generated 2026-02-13 18:42 using Cyotek HelpWrite Professional version 6.20.0