Start by naming the defect. An image that is already in focus but looks flat needs sharpening. A photo smeared by camera movement needs deblurring. A forwarded image may need compression cleanup, while a noisy low-light photo needs a balance of denoising and edge preservation. Increasing resolution is a separate task and does not automatically make the original capture clearer.
The best source matters more than the tool. Use the original camera file, export, or highest-quality scan whenever possible. A screenshot, thumbnail, or repeatedly forwarded copy contains less genuine texture, so every method has less evidence to work with. Keep the original untouched and export each experiment as a new file.
The short answer
Start with an AI online clearer when you want a quick diagnosis-free preview. Choose Photoshop for selective, professional control; GIMP for free desktop control; a phone app for a mobile-only workflow; and a dedicated sharpener when the image is already in focus and only the edges need help.
Make Image Clearer Online