Two words for basically the same thing. I’m definitely guilty of using both terms interchangeably which probably isn’t helpful for someone trying to get their head around cloth nappies.
Both an insert and a booster are there to absorb wee. And that’s really all you need to know. If we’re going to get into it then an insert is the main absorbent component of your nappy, so for something like an all-in-one this is the absorbent part attached to the PUL (waterproof outside layer). Or for a pocket nappy the insert is the main thing you are stuffing into that pocket. A booster is something separate that is used in addition to the insert to boost the absorbency. Some nappies come with boosters as well as the main insert part, some do not. Pretty much all nappies are designed to have a booster (of whatever brand etc.) added to them. A good booster can turn a nappy from a leaky nightmare to a reliable one.
But the different words really aren’t anything to worry about. They just absorb wee.
Inserts come in loads of different shapes and sizes. I’m going to run you through some of the ones I have in my stash. They all effectively do the same job and the shape makes little to no difference on the performance.
For some inserts you can adjust the way you use them to get better performance, where this is the case I have added additional photos.
The most common of all inserts. This is just used as is. It will normally fit which nappy it came with extremely well, but you’ll find these a very universal fit for most nappies.
The vast majority of pocket nappies come with a standard rectangle inserts.
As the name suggests this insert is shaped like an hourglass. It gives a bit more width at the front and back, going narrower between the legs. This is also used as is. Some will have poppers if they are part of an Ai2 nappy.
This is basically a long piece of fabric (in this case cotton) which is the width of the nappy.
The temptation is to just fold this insert in half. That will probably fit the length of the nappy nicely. This will give you two layers of absorbency. But by adjusting the fold slightly we can give an extra layer of absorbency, in the right place, improving the performance. I call this the Z-fold.
Nappies like this: Blueberry Diapers Deluxe.
Kind of a cross between the hourglass and the snake. This is a longer insert that fans out at one end. It will be too long for the nappy and will need folding.
Depending on the thickness of the insert you could try folding it in the Z-fold like the snake insert above. This particular one of mine is a bit too thick and a little short to be able to fold part of it into thirds. So in this case I just fold in half. For a boy I put the wider part at the front as it will provide more absorbency, for a girl I’d put the wider part at the back (although for a tummy-sleeper it may still be better off at the front).
Nappies like this: Designer Bums.
A tri-fold is a flat piece of fabric, they are rectangular in shape but more square than a normal rectangle insert. Just like a prefold. These are designed to be folded into thirds to create that standard rectangle shape. The reason they are able to be unfolded is to speed up drying time. Rather than sandwiching several layers of fabric together these allow those layers to be separated. The downside of this is the insert tends to be a bit bulkier.
As mentioned above boosters are something you can add to your nappies to increase absorbency. Typically they are a rectangle shape and a similar length to a nappy.
Again how you use your boosters will effect how well they work. Folding the booster in half will of course double its absorbency and you can concentrate this to where you need it most (front for boys, middle for girls). In nearly all cases I will fold my boosters in half, the only exception would be if this makes the nappy particularly bulky.
The booster pictured is my absolute favourite, an Easy Peasy hemp booster. Super slim and very absorbent.