BT.2020 (also "Rec. 2020") is the wide-gamut colour space introduced for 4K and 8K UHD broadcast. Where BT.709 covered ~36 % of all visible colours, BT.2020 covers about 76 % — more than twice as many. That's how a sunset on a BT.2020-mastered 4K stream can show fiery oranges and deep purples that look washed out on BT.709 — the BT.709 simply doesn't have those colours in its vocabulary.
The catch: no consumer TV can fully display BT.2020 yet. The best premium OLED and Mini-LED sets in 2026 reach about 70–80 % of the BT.2020 gamut, and most mid-range TVs sit around the smaller dci-p3 palette. The colour space is "aspirational" in that sense — content is mastered to fit inside BT.2020, displays gradually catch up year by year.
BT.2020 is closely tied to HDR: HDR10, HDR10+ and Dolby Vision all use BT.2020 as their colour space. If you're producing 4K HDR for streaming, you're producing in BT.2020 by default. SDR content doesn't generally need BT.2020 — it's overkill, complicates the production pipeline, and 95 % of the additional colours wouldn't display correctly on the audience's screens anyway.
