What counts as late at ALG
For transport purposes, anything after about 10 PM starts to get quieter. By midnight, the bus service has stopped and the number of taxis waiting outside drops significantly. Some international flights, particularly from the Gulf and France, arrive between 11 PM and 2 AM, so you will not be the only person in the terminal, but options narrow.
What is still running
Taxis continue to operate, but with fewer cars available. You may need to wait 10-20 minutes for one, and drivers who work late hours tend to quote higher prices since they know you have limited alternatives. The bus service (ETUSA) does not run late at night. Yassir (the local ride-hailing app) may have some drivers available but response times can be long.
What to expect inside the terminal
The terminal stays open for arriving flights. Immigration operates around scheduled arrivals, so you will not be stuck at passport control. The ATMs and exchange counters near arrivals may or may not be staffed depending on the hour. If you need cash, try the ATMs - they work 24 hours in theory, though machine availability is not guaranteed.
The honest recommendation
If you know you are landing after 10 PM, arrange transport in advance. A pre-booked transfer means someone is there with your name, regardless of the hour. This eliminates the two main late-night problems: finding a driver and negotiating a fair price when you have no leverage.
Safety considerations
The airport is safe at night. There is security throughout the building. The immediate airport area is also fine. The drive into the city at night is generally uneventful - traffic is light, which is actually an advantage. The main risk is not safety but simply inconvenience: waiting for transport that may not come quickly.
Hotels near the airport
If your onward journey can wait until morning, there are hotels within a 5-10 minute drive of the airport. The area around Bab Ezzouar has several options. You would still need a taxi to reach them, but the fare is short and cheap. This can be a sensible plan if you arrive very late and your final destination is far from the airport.