Xiaomi Redmi 9 (Prime) review

Display

The Redmi 9 features a large 6.53" IPS LCD with a waterdrop-shaped notch at the top to make room for the selfie camera. The resolution is extended 1080p - 2,340 x 1,080 pixels - making for a 395ppi density.

It is quite rare to see a 1080p screen on a budget device and the Redmi 9 is probably among the few cheap phones to offer it.

The display is protected with a Gorilla Glass 3, but this Redmi also ships with a thin screen protector that's been applied in the factory.

The Redmi 9 screen omits support for HDR10, wide-gamut color is not available, too. The phone has Widevine L1 DRM support though and you will be able to enjoy 1080p content from all popular streaming apps.

Xiaomi promises 1500:1 contrast ratio for the Redmi 9 screen, and our measurements show it is in the ballpark of the promised value.

Unfortunately, the maximum brightness is poor for an LCD at about 330 nits. However, the screen can go brighter if you leave it on Automatic Brightness - it can light up as high as 420 nits in bright ambient light - not much of an improvement, but that's about what Xiaomi is promising in the official specs, so not that of a surprise.

The minimum brightness we recorded on the white color is 1.4nit - a perfect one for reading sessions in the dark!

Display test	100% brightness
	Black,cd/m2	White,cd/m2	Contrast ratio
Xiaomi Redmi 9	0.202	328	1624:1
Xiaomi Redmi 9 (Max Auto)	0.253	426	1684:1
Xiaomi Redmi Note 9S	0.303	421	1389:1
Xiaomi Redmi Note 9S (Max Auto)	0.42	575	1369:1
Xiaomi Redmi Note 9	0.298	370	1242:1
Xiaomi Redmi Note 9 (Max Auto)	0	466	∞
Xiaomi Redmi Note 8T	0.331	450	1360:1
Xiaomi Redmi Note 8T (Max Auto)	0.453	600	1325:1
Realme 6i	0.328	528	1610:1
Samsung Galaxy A21s	0.317	408	1287:1
Samsung Galaxy A21s (Max Auto)	0.384	491	1279:1
Realme 5	0.345	485	1406:1
Realme 5s	0.345	487	1412:1
Sony Xperia 10 II	0	379	∞
Sony Xperia 10 II (Max Auto)	0	520	∞
Huawei P40 Lite	0.425	461	1085:1
Huawei P40 Lite (Max Auto)	0.501	515	1028:1

Xiaomi offers three different Contrast settings for the Redmi 9 display. With the Automatic contrast set to on, the screen has mediocre accuracy in the sRGB color space - we measured an average deltaE of 6.7 and maximum deviation of 15.1. Only in this mode, you can choose the color saturation (default, warm, cool) and the deltaE of 6.7 was measured with the Default preset. Choosing warm will diminish the massive blue tint and will lower the average deltaE to 5.2.

The Standard Contrast setting has somewhat better accuracy within the sRGB color space, and we recorded an average deltaE of 4.5 - still not a great one but it does help reducing the blue tint more.

Finally, the Increased Contrast makes the colors pop at the expense of reproduction accuracy.

Battery life and charging

The Xiaomi Redmi 9 is powered by a large 5,020mAh Li-ion battery. It supports 18W quick charging, but it only ships with a 10W adapter. Using the charger in the box will get a flat battery up to 20% in 30 mins - far from impressive. If you purchase an 18W (or more) USB-PD compatible adapter, you can get about 33% of the Redmi 9's battery filled in half an hour.

The Redmi 9 scored an outstanding endurance rating of 131 hours in our battery life test. The phone shows impressive times across the board - talk time, video playback and web browsing, as well as standby.

Our battery tests were automated thanks to SmartViser, using its viSerDevice app. The endurance rating above denotes how long a single battery charge will last you if you use the Xiaomi Redmi 9 for an hour each of telephony, web browsing, and video playback daily. We've established this usage pattern so that our battery results are comparable across devices in the most common day-to-day tasks. The battery testing procedure is described in detail in case you're interested in the nitty-gritty. You can check out our complete battery test table, where you can see how all of the smartphones we've tested will compare under your own typical use.

Speaker

The Redmi 9 has no special treatment for its loudspeaker. It is a single bottom-firing unit and tuned mostly for mid-tones. It posted a 'Good' result for loudness in our seven-track music test. It lacks a low-frequency thump, but it handles vocals decently.

Use the Playback controls to listen to the phone sample recordings (best use headphones). We measure the average loudness of the speakers in LUFS. A lower absolute value means a louder sound. A look at the frequency response chart will tell you how far off the ideal "0db" flat line is the reproduction of the bass, treble, and mid frequencies. You can add more phones to compare how they differ. The scores and ratings are not comparable with our older loudspeaker test. Learn more about how we test here.