都
dōu
Emphasising quantity with "dou"
都 reinforces any subject that already implies a group.
大家 / 很多人 + 都 + Verb
How it works
很多地方都有 wifi — lots of places have wifi. English wouldn't repeat "all" here; Chinese wants the 都 anyway.
The rule of thumb: if the subject is 大家, 很多人, 每个, 所有 or a doubled measure word, expect a 都 before the verb.
Examples
hěn duō dì fāng dōu yǒu miǎn fèi de wǎng luò
很多地方都有免费的网络。
Lots of places have free wifi.
dà jiā dōu tóng yì le
大家都同意了。
Everyone agreed.
wǒ de péng yǒu dōu xǐ huan tā
我的朋友都喜欢他。
All my friends like him.