At what redshift did cosmic microwave background radiation decouple from matter?

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Oval map of the cosmic microwave background radiation from NASA's WMAP mission, showing a mottled pattern of blue, green, yellow, and red representing temperature variations. — Cosmic microwave background A full-sky map produced by the Wilkinson Microwave Anisotropy Probe (WMAP) showing cosmic background radiation, a very uniform glow of microwaves emitted by the infant universe more than 13 billion years ago. Color differences indicate tiny fluctuations in the intensity of the radiation, a result of tiny variations in the density of matter in the early universe. According to inflation theory, these irregularities were the “seeds” that became the galaxies. WMAP's data support the big bang and inflation models, and cosmic microwave background is at the farthest limits of the observable universe.

The cosmic microwave background (CMB) radiation decoupled from matter at a redshift of approximately 1,090.123

This event occurred about 380,000 years after the big bang, when the universe had cooled sufficiently—to a temperature of about 3,000 K—for protons and electrons to combine and form neutral hydrogen atoms. Prior to this process, known as recombination, the universe was filled with a hot, dense plasma that was essentially opaque because photons were constantly scattered by free electrons. Once recombination occurred, the universe became transparent to light, allowing these photons to travel freely through space as the cosmic microwave background.312