A little, yes. Nowadays the casino work with special pages for specific promotions. There are still casinos that use bonus codes.
Casino Bonus Codes Guide
It is quite common for some online casinos to have bonus codes that players need to enter in order to claim their bonus regardless of whether this is for the different types of welcome bonuses, such as deposit bonuses, or no deposit bonuses.
In some cases, bonus codes are even required for ongoing bonuses or promotions that you may find on offer at an online casino on a monthly basis, the most common of which often being free spins bonuses.
While bonus codes originally were not widely used by online casinos, these have started to be adopted by a number of new casino sites, though it ultimately depends on the strategy of the casino brand and what they feel might be best.
Because there are so many different types of bonuses available, sometimes having individual bonus codes for each one can help to distinguish between them. Usually, a bonus code is required to be entered by the player when they come to claim a particular bonus, regardless of which one it is.
If for example it it is a no deposit welcome offer where the player receives $10, it could be that the bonus code is as simple as '10 bonus' which refers to the fact that the player will get $10 credited to their casino account when they have entered it.
In addition, some bonus codes might only be required for a mobile casino site if for example, the online casino is doing an a/b test to see how this affects sign up rates, from their desktop site and mobile site. Sometimes, if a bonus is particularly good, players do not mind entering a bonus code and this is quite often the case for no deposit bonuses, where the player is getting free bonus funds without having to make a deposit.
The process effectively takes less than a minute and is perfectly simple to do regardless of whether you are on a mobile device or desktop.