Stretching is not resizing
Classic resizing spreads the same pixels over more space, which is why enlarged photos look soft. This reconstructs the detail instead.
Know which direction you need
Making an image smaller is free in any tool. Making it larger is where the model earns its credits.
Changing the shape is a different job
To change the aspect ratio rather than the size, use expand image. It adds scene instead of stretching it.
FAQ
How much larger can it go?
Four times the original in one pass. Run it again for more, but check the result.
Will it fix a blurry photo?
Partly. For blur specifically, use unblur image first, then resize.
What formats?
JPG, PNG and WebP up to 10 MB.