Let's first touch on the definition of 'custom' in this context, as it can vary greatly from platform to platform. For in-house solutions, it is generally everything that deviates from commonly expected behaviour. For widely used solutions like Joomla! or Wordpress, definition becomes less broad as someone somewhere has likely already required certain functionality, and may be available as an extension, or similar enough to be adapted.
One of the top reasons we use Joomla! as the platform of choice, is that it is extremely extendable, and that there are so many quality built extensions, that we can usually minimise what would be the 'custom' component of a project, or even eliminate it altogether.
Over the years we developed a few custom applications, some with little bit of custom programming, some with a lot, and some with completely custom built solution but without much programming. All of these methods serve one purpose, reducing the cost of production, while remaining a robust product. Sometimes a project may be so specific, that nothing like it has been developed anywhere as yet, but we'll do our best to think of a way to make it less demanding.
The only sure way is to get in touch and describe as best and detailed as possible what it is you need, we'll be happy to turn the think tank mode on. In the meantime, below are two radical examples of how 'custom' can be subjective.
A few years back I was approached by a distributor dealing with power cells, consumer, car, boat and other batteries, solar panels, wind turbines and other related products. They had trouble finding a developer or an agency that could build them a solution they needed. It was quite a large project and their requirements were numerous, but not particularly odd. They were however until that point told by all, that their requests require a completely custom built solution, the cost would be in six figures, and even that certain requests were not possible to be met at all.
Having analysed the project, and throwing in a pinch of out-of-the-box thinking, it became obvious that it wasn't to dissimilar from another project I built for a different purpose altogether. This allowed me to come up with the architecture for the complete project, and offer them a purpose built turn-key solution based on the Joomla! platform, with all their requirements met, and at a lower cost. In the end, the only custom segment of the project was the approach to content preparation with zero custom programming, and they got exactly the solution they needed, and were very happy with.
In 2021, while working for an agency, I was called in to assist Wordpress developers with programming customisations they need. The project was an accommodation booking web site, and the request was so simple, I thought they're playing a prank. They needed for users to be able to have not only select type choices, but checkbox ones as well. Solution was built on Wordpress, the top rated plugin for bookings purchased to make the project with, the WP team built it all and everything was great, except for that request.
Turned out that no booking solution supported checkboxes, including that one. We've all been to booking sites, we know you can select added features such as pool, playground, tennis court or what not, as a checkbox. Adding it in is a most basic of tasks, but as is often the case, their plugin overwrote WP native functions, and so standard approach wouldn't work. Support from the plugin developers was nonexistent, it's custom, they don't support it, and they don't provide developer manuals. Long story short it was done, but a simple 30 minute task took hours of analysis and debugging before a few lines of code could be added.
Please note, custom programming is available for PHP language only, and we do not offer custom programming for projects not done by us, no matter the platform.