I have traveled back and forth to Istanbul for dozen times, sometimes just by a connecting flight, sometimes just to spend a day or two in Istanbul. Most of the time, I have relied on shuttle services ordered from hotels or using public transportation.
The last time when we visited Istanbul, via Sabiha Gokcen airport (May 2023) I noticed the price for one way transfer to the city center was EUR 60 (a few years ago I paid USD 40 for the same ride). This time I decided to check if there is a taxi app for Istanbul, like Bolt or Uber.
I'm not sure if is there an Uber service available in Istanbul, but I found the BiTaksi app and I was pleasantly surprised to learn that with this ride-sharing app, the prices are much lower compared to the shuttle services or trying to catch a street taxi. Catching a street taxi as a foreigner in Istanbul might cost you 4 times higher than the actual price.
Sure the name might sound a bit akward - BiTaksi, not sure did the developers of the company were aware of the meaning or it's just me, but the service was quite straightforward.
I was able to add my Visa card and for most of the rides was paying using it.
Also make sure you have permanent internet access, as several times I was not able to pay by Visa card as my foreign bank was not sending me sms code for confirmation. I had to pay in cash (bring some cash also, just in case things dont work as expected)
Using this app we traveled quite a lot around Istanbul, like going from our hotel to Vialand and back, going to Forum Istanbul shopping mall and back, and also going to Sabiha Gocken airport. for Sabiha gocked anirport I paid 670 TRY / around USD 33 / EUR 30.
It seems at the momement BiTaksi ride-sharing app is available in Istanbul and Izmir.
In overall great expierience, little waiting times, polite drivers, not engaging in meaningless conversations. Highly recommend!