A necessary update is coming for PDF readers and open-source libraries that handle document processing, as they will all need to support the new Brotli compression filter.
Brotli stands as one of the most widely adopted yet often unrecognized compression formats, having been integrated into all major web browsers and content delivery networks (CDNs) for an extended period. Despite its pervasive use, it has not yet been applied to the creation and display of PDF documents. Since version 1.2 in 1996, PDFs have traditionally relied on the FlateDecode filter, which is also utilized for compressing .zip and .png files.
This situation is set to change. The PDF Association is nearing the release of a specification this summer, which developers can implement to integrate Brotli into their PDF processing tools. The expectation is that Brotli will then be rapidly incorporated into an updated version of the official PDF 2.0 standard, ISO 32000-2, which is overseen by the International Organization for Standardization.
As PDF file sizes continue to grow, and enterprises store billions more documents in their data lakes annually, the demand for a more efficient compression method has become critically urgent.
Adopting Brotli compression will yield a significant benefit: smaller PDF files. This is projected to result in an average reduction of 10% to 25% in file size, the exact percentage depending on the specific content being encoded, as demonstrated by a 2025 test conducted by Artifex Software, a PDF Association member.
However, for businesses, this marks the beginning of a significant undertaking. Once PDFs compressed with Brotli start circulating, any users who have not updated their applications and associated libraries to support this new format will be unable to decompress and view these files. This would be unprecedented for PDFs; while the format has gained many features since becoming an ISO standard in 2008, none have prevented users from opening existing PDF documents.
Among the most prominent software requiring an update for Brotli support are proprietary PDF creation and reading tools like Adobe Acrobat, Foxit PDF Editor, and Nitro PDF. Browser-integrated PDF readers are also included in this category.
Beyond these primary applications, a vast ecosystem of less visible open-source utilities, libraries, and SDKs is extensively used within enterprises for PDF workflows and automated batch processing. Identifying and updating these components, which are often deeply embedded within third-party libraries, is expected to be a time-intensive process.
Should enterprises postpone these updates, they risk encountering Brotli-compressed PDFs created with newer software that will fail to open on their outdated programs. IT teams are most likely to face this challenge when users contact them reporting file access issues.
Integrating Brotli Support
To initiate widespread adoption, developers require encouragement, stated Guust Ysebie, a software engineer at document processing developer Apryse. He remarked, “Someone needs to take the lead and generate buzz to inspire other products to follow suit.”
This presents a challenge because, as he explained in a post on the transition to Brotli on the PDF Association’s website, Brotli’s integration has been hindered by the PDF specification’s requirement for consensus among hundreds of stakeholders.
He proposed three strategies to facilitate this transition. The most straightforward is to extensively publicize the need for upgrades across various information channels as part of a broad awareness campaign.
A more unconventional suggestion involves formatting Brotli-enabled PDFs so that instead of causing older readers to crash, they display a “not supported” error message. This message would then prompt users to upgrade as a substitute for the inaccessible compressed content.
A final approach is for like-minded developers to proactively update open-source libraries themselves. Ysebie mentioned that he has already incorporated Brotli support into several libraries, including the iText SDK from Apryse.
“This is the real-world mechanism for adoption: an unofficial feature is created, early adopters implement it, which then encourages larger products to follow suit,” Ysebie explained. The pivotal moment for Brotli-enabled software adoption will be its integration into Adobe Reader. While this is expected to happen eventually, the exact timing remains uncertain, he added.
The positive news is that because only a limited number of software libraries require upgrades, adding support to these programs should be relatively simple, Ysebie noted. However, organizations will still need to apply these updated versions to their existing applications.
Regarding when Brotli will be formally incorporated into the ISO PDF 2.0 specification (a process ongoing since 2015), Ysebie acknowledged that there is still a considerable path ahead. However, he emphasized the industry’s need to progress beyond older technologies. “We must advance the ecosystem. It may initially be a bit chaotic, but the future potential is immense.”
