Firefox 156 Released with Faster PDFs and Lighter JPEGs

Mozilla released Firefox 156, the new version of its desktop browser, by September 16, 2026. It is the second release since the move to a biweekly release cycle. With new features held back, the focus is on improvements that increase responsiveness and efficiency in real-world use.

Reporting by EditorDavid on Slashdot highlights shorter startup times for the built-in PDF viewer and reduced processing load for large JPEG images as the main changes. The original text explains it as follows.

In Firefox 156, the browser now uses libjpeg-turbo’s IDCT scaling to reduce images during decoding, rather than loading a full-size image into memory and then shrinking it.

The same report also covers the expansion of sponsored suggestions to more regions and how AI features are controlled. This is a release to watch for how Mozilla balances development speed and quality maintenance after changing its release cycle.

Faster Built-in PDF Viewing and How It Works

In Firefox 156, startup of the built-in PDF viewer is up to 45% faster. The PDF.js-based viewer needed to launch a background worker process each time a document is displayed. Because it was previously launched only when needed, there was a wait on first display.

In the new version, loading of the background worker has been moved earlier. Preparation proceeds in parallel with the action of opening a document, reducing perceived delay. The change to the mechanism itself is hardly visible to users. It is an optimization that reorders the startup steps.

The PDF viewer is used frequently for business documents, administrative procedures, and academic materials. Even if the startup time reduction is only a few hundred milliseconds per instance, it affects productivity with repeated use. It can be seen as an improvement that increases reliability as a standard browser feature.

Mozilla has integrated accessibility features into the PDF viewer, such as automatic generation of alt text for images. Faster startup also lowers barriers to using these accompanying features. If display is fast, users are more likely to try accessibility features. Improving base performance is a prerequisite for wider adoption of features.

More Efficient Large JPEG Decoding and Its Effects

Display processing for large JPEG images has also been made more efficient. The new version uses libjpeg-turbo’s IDCT scaling to downscale images during decoding. Previously, full-size images were expanded into memory and then shrunk. Eliminating steps reduces wasteful memory consumption and computation.

Measurements attached to the bug report showed cases where decoding speed reached up to about twice as fast. Reduced memory usage when loading very large images was also confirmed. An already fast process has been made internally more efficient. This is not the kind of change users will clearly notice on screen.

Technically, it is a method that scales down at the stage of discrete cosine transform coefficients. It extracts only the resolution needed for display without restoring all pixels. It is effective when viewing high-resolution images such as shared photos, map images, and e-commerce product images. It is a concept that could also be applied to shared architectures with mobile devices.

More efficient image processing also helps curb power consumption. Shorter CPU run times reduce heat generation and battery drain. While the difference is slight for a single image, it accumulates for users who view images frequently. It is also a meaningful improvement from the perspective of environmental impact.

Address Bar Suggestion Feature Expands to

More Regions

Sponsored suggestions in the address bar have been enabled in France, Germany, and Italy. This extends a system already introduced in other regions to major European countries. Suggestions from sponsors are displayed along with candidates matching the partially typed text.

They can be disabled in Settings. In the Search section of Settings, under Firefox Suggest, users can turn off suggestions from sponsors. Users in regions where they are enabled by default must manually disable them if they are not needed. It is important that the location of the option is clear.

The suggestion feature is one of Mozilla’s sources of revenue. Income from search partnerships supports its development structure. At the same time, concerns remain about the handling of users’ activity history and input. With the regional expansion, the display conditions and how to disable the feature need to be clearly communicated.

Europe is a region with strict privacy regulations. Enabling the feature in France and Germany will be a test of both regulatory compliance and user acceptance. The focus is on whether transparency of sponsored displays is ensured. It is expected to inform decisions on future rollouts in other regions.

Centralized AI Controls and Preserving Choice

Mozilla has stated a policy of letting users choose how they engage with AI features. A new AI Controls section in Firefox’s General Settings allows users to block current and future AI features and related notifications all at once. The design lets users reflect their preferences without navigating through individual settings screens.

Individual controls cover AI translations, alt text in the PDF viewer, tab group suggestions, and link previews. Each can be turned on or off by use case. The setup meets the needs of users who fall between total rejection and total acceptance.

The browser industry is increasingly embedding AI assistance. There are many cases where conversational assistance, summarization, and automatic categorization are enabled by default. Against this backdrop, an approach that combines bulk blocking with individual choice is distinctive. As Cloudflare AI Gateway Adds Per-User AI Usage Limits shows, interest in managing and limiting AI usage is also growing on the infrastructure side. User-side controls and provider-side management are advancing in parallel.

As a top-level integrated feature, Smart Window is being tested. The concept is to support continuity of work using only context users have permitted to share, such as open tabs and browsing history. It is described as designed not to send context externally without permission. Publishing implementation details and verification results remains a future task.

Outlook for JPEG XL Support in the Next Release

Firefox 157 is expected to be released in about two weeks. According to PCWorld reporting, support for JPEG XL is expected to be included. JPEG XL is a still-image format standardized in 2021 that can retain quality equivalent to JPEG at smaller file sizes.

Safari is said to be the only browser with formal support at present. Chrome supported it for a time but removed support in 2022. Vendors have diverged in their decisions amid debates over encoding efficiency, decoding load, patents, and operational outlook.

If Firefox adds support, creators will have more options. More supporting browsers will reduce the need for dual management of image delivery. Smaller sizes directly curb transfer volumes and storage costs. The effect will be particularly large for media and stores with many images.

However, wider adoption of the format also requires support from encoding tools and delivery networks. As seen in Cloudflare Strengthens Vite/Astro Development with VoidZero Acquisition, the readiness of build tools and delivery infrastructure influences developer adoption. An image format alone will not spread widely. It must be evaluated together with the surrounding tooling.

This release, 156, reduces the burden of the current format by making large JPEG processing more efficient, paving the way for the next-generation format in the next release. It is a sensible sequence to support a gradual transition. It can be seen as an effort to balance stability and future readiness in image display.

Editorial Opinion

In terms of short-term impact, we expect faster PDF viewing and more efficient JPEG decoding to boost evaluations for enterprise adoption over the next three to six months. Each item is modest, but they help with repetitive daily work. Centralized AI controls will also make it easier to set management policies. Checking default settings and updating deployment guidelines will be practical challenges. We believe they will also be used as material for comparison with competing browsers.

From a long-term perspective, the design of AI choices and support for image formats will be turning points. Over one to three years, combining bulk blocking with individual choice will affect user trust. If JPEG XL support is realized, it will change encoding strategies for delivery providers. Media that must both reduce size and maintain quality will be most affected. We expect broader standards support to change production workflows.

Remaining questions from the editorial team concern measured efficiency gains and the effectiveness of choice. The benefit of faster decoding varies with image dimensions and device performance. Verification is needed of the conditions under which differences appear. Operational confirmation is also needed on whether bulk AI blocking will reliably cover future features. The scope of context use in Smart Window is also unclear from public information alone. We believe transparent measurement and documentation are required.

References

• “Firefox Touts Lower CPU Use for Large JPEGs, Faster PDF Viewer Startup (and AI Controls)”, by EditorDavid — Slashdot, 2026-09-16T13:04:00.000Z (ARR)
• Source URL: https://news.slashdot.org/story/26/09/16/0352217/firefox-touts-lower-cpu-use-for-large-jpegs-faster-pdf-viewer-startup-and-ai-controls?utm_source=rss1.0mainlinkanon&utm_medium=feed