Version: Unity 6000.0.31f1
When creating games or apps in Unity, you’ll often encounter situations where you need to replace images later.
For example:
- You used placeholder images during prototyping but now want to replace them with final designs.
- You want to replace a group of UI buttons or icons all at once.
- You want to safely replace images while preserving scene references.
This article explains the “safe replacement method” where people often stumble, and “precautions when replacing images with different sizes.”
1. How to Safely Replace Images in Unity (Basic Edition)
1-1. Methods of Replacement That Should Not Be Used
When you try to replace an image by dragging and dropping it directly into the Project window, the system automatically appends “1”, “2”, etc. to the end of the filename.
As a result, you end up having to manually correct them all.
1-2. Correct Replacement Method
The safest method is to overwrite files outside of Unity.
- Open the Assets folder using Finder (Mac) or Explorer (Windows).
- Save the new image with the same filename as the one you want to replace.
- Right-click the image in Unity and click Reimport, or restart Unity. The image will automatically update.
This method allows you to safely replace files.
To locate the folder, click Reveal in Finder from the top menu bar under Assets.
1-3. Key Points When Replacing
- Keep filenames the same → Unity can update while maintaining correct references
- Unify formats (PNG/JPG, etc.) → Prevent unnecessary re-import issues
2. Points to Note When Replacing Images of Different Sizes
Replacing images of different sizes does not work properly. For this 200×200 pixel image,
Replacing it with a 100×100 pixel image resulted in an error. A warning is displayed.
The issue occurs because Unity attempts to maintain the previous sprite settings when the original image is replaced, but fails due to the size change.
Conversely, if you replace a 100×100 pixel image with a 200×200 pixel image, only part of the image will be displayed.
Countermeasures
Open the Sprite Editor in the image inspector.
Set the image range correctly.
If possible, select Apply in the upper-right corner and close the editor to display everything.
How to handle replacing with a smaller image
If the image turns white after replacing it with a smaller one, opening the Sprite Editor will display this dialog. Select Resize here.
Set the image range and click Apply to display it correctly.
Summary
- The safest replacement method is to overwrite files with the same name outside of Unity.
- If sizes differ, adjustment in the Sprite Editor is required.
- Ideally, matching the replacement image size is best.
By keeping these points in mind, you can safely replace images in your Unity project.
