The flatten image and merge layer commands do the same action: they turn two or more layers into one. However, they do this in different ways, which can be good or bad, depending on why you want to combine your layers. You can easily decide which action to do when you know the difference between flattening images and merging layers in Photoshop.

The difference between Flatten Image vs Merge Layers in Photoshop is that Flatten Image will combine all visible layers without preserving transparency and will delete any hidden layers. Merge Layers will combine any two or more selected layers into one while preserving transparency.

Now let’s take a closer look at these two options to understand their advantages and disadvantages better along with when to use each one.

What Is Flattening An Image In Photoshop?

The Flatten Image command in Photoshop turns all layers in the Layers panel into one background layer. To flatten an image, right-click (Win) or Control + click (Mac) on any layer and select Flatten Image.

Layers before being flattened

Layers after being flattened

When you flatten layers with transparent areas, Photoshop fills those areas with white. It also locks the resulting layer. In the example above, my layers had transparent backgrounds, so the resulting image gained a white background.

The Flatten Image option doesn’t require you to select any layers since it instantly flattens all layers in the Layers panel, except for the non-visible ones. That can be a time saver if you are confident this is your best option. 

When you leave a layer hidden, the Flatten Image command deletes it. In the example below, I left the pink circle hidden.

When I tried to flatten my layers, Photoshop asked me if I wanted to discard the hidden layer because that’s what the Flatten Image function does by default.

After flattening layers, you won’t be able to edit their elements individually unless you undo the action by pressing Control + Z (Win) or Command + Z (Mac). The History panel also allows you to reverse the action.

Pros and Cons of Flatten Image

Pros

  • Combine layers instantly, which can save you time
  • Reduce the file size for print

Cons

  • Doesn’t preserve layer transparency
  • Discards hidden layers
  • Doesn’t let you choose which layers will be flattened
  • You can’t edit layers individually after flattening them

What Does Merging Layers Do?

Have you ever had so many layers in the Layers panel you lost track of them? It turns out that in many cases, you can combine elements instead of occupying individual layers. For example, if you have two layers with the same geometric shape and need to apply the same adjustments to them, why keep them in separate layers?

Assuming you don’t need to edit or drastically resize the shapes, that is.

When layers should be combined but aren’t, they can cause several problems. For example, your Layers panel becomes disorganized and confusing. Additionally, these extra layers may overload your computer’s memory. That’s when the Merge Layers command comes in handy because it turns two or more selected layers into one individual layer.

The only downside of this option is that when you merge layers, you can no longer edit them individually. That’s because each adjustment you apply to the merged layer will be applied to the layer as a whole. It will also turn any vector layers such as type or shape layers into rasterized layers which aren’t always ideal.

To merge layers, you have to select them one by one, unless you want to merge all visible layers, which is also possible. As a result, you can control which layers are combined and which ones are left untouched.

Another advantage of merging layers is that it preserves transparency. So you don’t need to worry about your layers being filled with random background colors when combining them.

To merge layers, select the layers to be merged, then right-click (Win) or Control + click (Mac) and select Merge Layers.

Layers before being merged

Layers merged

Keep in mind that the Merge Layers option names your resulting layer after the layer at the top of the selected layers. Then, it is up to you to rename the resulting layer. 

Additionally, when merging layers, non-visible layers are ignored and left untouched if you select Merge Visible.

Layers before being merged. Notice that there is one hidden layer.

Layers after being merged. The hidden layer is preserved.

Pros and Cons of Merge Layers

Pros

  • Makes the Layers panel more organized by turning two or more layers into one
  • Preserves layer transparency
  • Only combines selected layers
  • Does not discard hidden layers

Cons

  • After merging layers, you can no longer edit them individually

Is It Better To Use Merge Layers Or Flatten Images In Photoshop?

You are more likely to find yourself in situations where you need to merge layers rather than flatten images. That’s because the Flatten Image command is used for specific cases where you want to combine all layers in the Layers panel into one, which is usually done at the end of a project if the project size is too large.

The Merge Layers command, on the other hand, allows you to choose which layers to combine, giving you more control over what layers stay and what layers merge in the Layers panel. Additionally, this function does not prevent you from continuing working on your project, as you should only be combining layers that can be edited together.

In the end, there is no better or worse option. You just need to choose the one that best aligns with your intentions in a given moment.

Do You Need To Merge Or Flatten In Your Projects?

The decision to merge layers or flatten images depends on which stage of a project you are in.

Flatten Image is recommended when you have finished your project and want to turn all layers into a background image, as you no longer intend to continue editing them. This way, you can export the finished picture and use it in any way you want. 

On the other hand, you should Merge Layers when you are in the middle of a project and want to get rid of extra layers because you know that some layers can be combined instead of taking up extra space both in the Layers panel and on your computer. This way, you can keep working on your project in a more organized workspace.

However, it’s not necessary to flatten your image or merge your layers at all. If your Layers panel is organized and you need to keep each layer separate to create separate edits, it’s perfectly okay not to use either of these actions.

If you are in a situation where you want to organize an excess amount of layers but don’t want to lose out on the ability to edit them, you can use smart objects instead of merging or flattening.

Happy Editing!