ABR rate control — Average Bit Rate — is the encoder mode that targets a specific average bitrate over the whole video while letting individual frames and scenes vary. You tell the encoder "aim for 4 Mbps overall", and the encoder spends more bits on hard scenes (action, snow, water) and fewer on easy ones (talking heads, static backgrounds), balancing out to the target. It's the sensible middle ground between strict cbr (constant bitrate, wasteful) and quality-first crf (whose bitrate is unpredictable).
A small clarification because the same letters mean different things in streaming. The "ABR" used in rate control (this article) is one thing — an encoder setting. The "ABR" used in delivery — Adaptive Bitrate streaming, the HLS/DASH technique of giving each viewer the rendition that fits their network — is something different entirely. Both abbreviate "average/adaptive bitrate" but they live in different parts of the pipeline. Most engineers use context to disambiguate; vendor docs sometimes do too.
For a product team, ABR rate control is the default for VOD pipelines that need predictable file sizes. You know what your CDN bill will be because you set the average bitrate per rendition; you get smarter bit distribution than CBR. The downside is that the encoder doesn't see the entire video ahead of time in single-pass mode, so the bit distribution isn't optimal. Two-pass ABR fixes that — first pass analyses the video, second pass encodes — at the cost of doubling encoding time. In 2026 ABR is gradually being replaced by capped CRF, which targets quality directly and bounds the worst case; ABR survives mainly in pipelines built around fixed bitrate targets.
