The 65-year-old Bangladeshi national is a worker of Riyadh Municipality. He was mocked by an Instagram user who shared Karim's photo with the caption: "This man deserves to only look at rubbish."
Abdullah Al-Qahtani - whose Twitter account is named 'Ensaneyat', meaning 'humanitarian' in Arabic - tweeted about Karim to find him; the tweet was shared more than 6,500 times.
Eventually, Twitter users identified the cleaner's location by analysing the reflection of the shop window in the photo.
Karim's monthly salary is $187 (700 Saudi Riyal). He confirmed that he was not aware of the photo being taken.
Al-Qahtani has also received bags of rice, honey, return tickets to Bangladesh and two mobile phones - an iPhone 7 and a Samsung Galaxy - for Karim.
Netizens are still sending gifts for Karim; one user even wants to give him $530 (2,000 Riyal).
Al-Qahtani told
CNN that he was “impressed by the efforts made to locate the cleaner and by the kindness and generosity of those who reached out to help him”.