Errata
Here you can find comprehensive information about errata that affect our data releases, including crawl data, and web graphs. If you have any problems to report please Contact Us.
Redirect target URL in URL indexes may be a relative URL
When the HTTP “Location” header includes a relative URL, the corresponding “redirect” field in the CDX index and “fetch_redirect” field in the columnar index will also store a relative URL. In all other cases, redirect targets in the URL indexes should be recorded as absolute URLs.
Read More...Content is truncated
Some archived content is truncated due to fetch size limits imposed during crawling. This is necessary to handle infinite or exceptionally large data streams (e.g., radio streams). Prior to March 2025 (CC-MAIN-2025-13), the truncation threshold was 1 MiB. From the March 2025 crawl onwards, this limit has been increased to 5 MiB.
Read More...No truncation indicator in WARC records
Due to an issue with our crawler, not all truncations were indicated correctly. A workaround to detect length truncation is to be suspicious if the length of the content is exactly 1048576 bytes. Truncations for time or network do not have such a workaround. In the WARC files this indicator is called "WARC-Truncated".
Read More...Missing content_truncated flag in URL indexes
The flag in our URL indexes (CDX and columnar) that indicates whether or not a WARC record payload was truncated was added in CC-MAIN-2019-47. This indicator is missing in our indexes for all previous crawl releases. In the CDX index this is referred to as "truncated", and the columnar index refers to this as "content_truncated".
Read More...SURT URLs do not properly encode non-UTF-8 percent-encoded characters
When constructing SURT (Sort-friendly URI Reordering Transform) URLs, percent-encoded characters that are not valid UTF-8 sequences were not being correctly handled. This could lead to inconsistencies in URL normalization and sorting, potentially causing incorrect deduplication or retrieval issues in datasets that rely on SURT-based indexing.
Read More...WAT data: repeated WARC and HTTP headers are not preserved
Repeated HTTP and WARC headers were not represented in the JSON data in WAT files.
Read More...WARC revisit metadata records
The revisit records in the Common Crawl WARC archives (since Aug 2018) lack the metadata record which is attached to all response records.
Read More...Erroneous title field in WAT records
The title field in WAT record is extracted from last but not first <title> element in an HTML page
Read More...Missing fetch_status fields
In our columnar index for this crawl, the `content_mime_type` is missing and `fetch_status` is always -1. In the cdx index (columnar: `content_mime_type`), fields "mime" and "status" are missing.
Read More...Redundant extra line in response records
The WARC files of the August 2018 crawl contain a redundant empty line between the HTTP headers and the payload of WARC response records.
Read More...Incorrect fetch_time metadata
The fetch_time metadata for robots.txt might be incorrect in some crawl releases.
Read More...Charset Detection Bug in WET Records
The charset detection required to properly transform non-UTF-8 HTML pages in WARC files into WET records didn't work before November 2016 (CC-MAIN-2016-50) due to a bug in IIPC Web Archive Commons.
Read More...ARC Format (Legacy) Crawls
Our early crawls were archived using the ARC (Archive) format, not the WARC (Web ARChive) format.
Read More...Missing Language Classification
Starting with crawl CC-MAIN-2018-39 we added a language classification field (‘content-languages’) to the columnar indexes, WAT files, and WARC metadata for all subsequent crawls.
Read More...Some 2–Level CCTLDs Excluded
A bad configuration was checked into our exclusion list on Sep 22, 2022 and was fixed on Oct 27, 2023. The configuration blocked a number of 2–level domains, meaning they were not included in certain crawls.
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