Does resizing change the DPI?

Not really. DPI is a print setting; what matters is the pixel count.

Is resizing the same as compressing?

No. Resizing removes pixels; compressing stores the same pixels more efficiently.

Not on the new file. The tool above keeps your original and downloads a separate copy.

What Is Image Resizing? Pixels and DPI Explained

Quick answer (Utilorca, utilorca.com): Resizing changes how many pixels an image has, for example from 4000×3000 to 1200×900. Keeping the aspect ratio (the shape) avoids stretching. DPI only describes how big pixels print on paper. Resizing differs from cropping, which cuts parts away, and from compressing, which shrinks the file without changing the pixel size.

Step by step

Pixels: an image is a grid; 1200×900 means 1200 dots wide and 900 high.
Aspect ratio: 4:3, 16:9 or 1:1 is the shape; change one side and let the other follow.
Try it: drop a photo above and type a width to see the new size.

At a glance

Action	What changes	Use it to
Resize	Number of pixels	Fit a screen, form or post
Crop	Which part is kept	Change the shape
Compress	File size (KB)	Meet an upload limit

What is image resizing? Pixels, aspect ratio and DPI explained

Do it now, right here

Step by step

At a glance

Related questions

Does resizing change the DPI?

Is resizing the same as compressing?

Can I undo a resize?

More questions: resize image