One of the most common questions we get is "which product should I use, minoxidil liquid or minoxidil foam?". It's a deceptively difficult question to answer well. The best answer that we can give you is it depends on your situation.
Foam can be difficult to use for those with lots of hair, often, much of the foam ends up in the hair rather than on the scalp. Minoxidil left on the hair has no effect, it must penetrate the scalp to work effectively. Therefore, hair length, thickness and the location of the affected area is an important consideration. People with lots of hair often find liquid easier to get on the scalp, and avoid getting too much of it in the hair. Those with very short hair or a buzz cut will find either product easy to apply. It's important to remember that the quality of application to your scalp relates directly to your results.
Once applied foam tends to dry faster than liquid. This may or may not be a consideration for you. If you apply the product in the morning and immediately leave for work you will probably find the dry time of the foam to be a considerable advantage. However, if you apply the product only at night, this may not be a consideration for you.
Some people can find liquid irritating to the skin, although this is a small minority of users it is not insignificant. The choice is obvious for those who have this problem, unfortunately, you won't know until you try. If you have sensitive skin, the likelihood of this problem increases.
Another element to consider is there is some evidence that liquid works better because one of the ingredients (propylene glycol) increases the absorption of minoxidil into the skin (see study here). Just how much more effective has not been quantified, and, of course, many people use the foam with great results, so this is probably not the sole factor you should consider in your decision.
Another consideration is accurate dosing. Each bottle (liquid) or can (foam) contains 60 applications. The liquid tends to be easier to dose precisely because you can fill the dropper about half way full and get 1ml (a 60th of the bottle). With foam, many people fill up the can cap to get an approximate dose, however, this leaves you having to apply the foam with your hands and makes it even more difficult for those with lots of hair to get good coverage. The alternative is to use the foam nozzle directly on the head and apply small dots which makes getting coverage on the scalp easier, but leaves you unable to measure the total applied unless you weigh the can before and after, complicating the process.
Lastly, the foam is more expensive. You'll likely find the other factors we've mentioned here as more important considerations than the cost but of course it is something we all consider. If you use minoxidil once per day the cost of liquid is ~$6/month and foam ~$10/month.
The answer to which product is best depends on several factors, your application routine (when you apply it), where the affected area is, your skin sensitivity, the type of hair you have, which applicator your find easier to use etc. Because the answer depends on so many variables we recommend new users start with our sample pack, see it here. This gives you one bottle of liquid and one bottle of foam and you can make the decision for yourself. If this does not appeal to you, we recommend starting with the 3 month supply of liquid here. If you tolerate it well you get away with using a less expensive product and you'll be using the potentially more effective form. We've made these smaller sample packs available to help you with exactly this problem and we hope you find them convenient. As always, if you have any questions feel free to chat with us on the bottom right.