Making an image smaller almost never hurts it
Here's the reassuring part most people don't expect: shrinking a photo is essentially free. Take a 4000×3000 image down to 1000×750 and the software discards fifteen of every sixteen pixels, yet the ones it keeps still describe the same scene — just packed more densely. A good downscale reads as crisp, sometimes even cleaner than the original, because fine sensor noise gets averaged away in the process.
The one real risk when going smaller is aliasing. Shrink too aggressively with a crude method and thin lines, fabric, or repeating patterns can break into jagged stair-steps or shimmering moiré. Quality software — including the resize tool here — avoids that by blending neighbouring pixels as it reduces size, so in normal viewing the loss is genuinely invisible. 'Resize without losing quality' isn't marketing copy when you're going down; it's just how downscaling works.
Resampling: what happens to the pixels you keep
Whenever dimensions change, every output pixel has to be computed from the input pixels around it. That process is called resampling, and the method matters. Nearest-neighbour simply copies the closest original pixel — it's fast and keeps hard edges perfectly, which is exactly what you want for pixel art or a screenshot of sharp UI, but it looks blocky on photographs. Bilinear averages the four nearest pixels (a 2×2 block) for a smoother but slightly soft result.
Bicubic samples a 4×4 grid of sixteen pixels and weights them by distance, giving noticeably sharper edges — it's the long-standing default for photos. Lanczos goes further still and usually preserves the most fine detail, at the cost of faint 'ringing' haloes around high-contrast edges. In a browser, a canvas set to high-quality smoothing uses a bicubic-class filter, which is why an in-browser resize can hold its own against what a desktop editor produces for the same photo.
Aspect ratio is what actually wrecks photos
If a resize ever leaves a face looking stretched or squashed, the culprit isn't the resampler — it's aspect ratio. Every image has a fixed width-to-height ratio, and if you change one dimension without changing the other proportionally, everything in the frame distorts. Type 800×800 for a photo that was 1200×800 and you've squeezed it 33% narrower, so every face in it gets visibly thinner.
That's why the resize tool offers three modes. Fit keeps the ratio and pads any mismatch with a letterbox (white by default), so nothing is cropped or stretched. Fill keeps the ratio and crops whatever overflows the target box. Stretch ignores the ratio entirely and forces the image to the exact numbers you type — occasionally handy, but the mode responsible for those unsettlingly wide portraits. When in doubt, leave 'Lock aspect ratio' ticked: set one dimension and let the other follow.
Resizing changes pixels; compressing changes bytes
'Resize' and 'compress' get used interchangeably, but they pull completely different levers. Resizing changes the pixel dimensions — a 1200×800 image becomes 600×400. Compressing keeps the dimensions and shrinks the file by encoding the same pixels more efficiently; a JPEG's quality slider is compression, not resizing.
The two solve different problems. If a photo is physically too big for a layout, resize it. If the dimensions are already right but the file is a heavy 4 MB, compress it — a 1200×800 JPEG at quality 80 typically lands in the low hundreds of kilobytes with no visible change. Lossy formats like JPEG and WebP discard detail your eye barely registers; PNG is lossless but larger, and it's the one to reach for when you need crisp text or transparency. Knowing which lever you need stops you from over-shrinking an image's dimensions just to make its file smaller.
When you actually need to go bigger
Everything above assumes you're staying at or below the resolution your camera captured. Going past it is a different story, because there is no honest way to add detail that was never recorded. Enlarge a 500-pixel image to 2000 pixels with ordinary resampling and the software just spreads the existing pixels — the result is bigger and softer, never genuinely sharper. This is the one case a normal resize can't rescue.
If you truly need more pixels — a small web image you want to print, or an old photo you want to enlarge — reach for the Upscale tool instead. It runs a compact Real-ESRGAN neural network (the general x4 model) trained on synthetic real-world degradation, so instead of merely stretching it reconstructs plausible edges and textures and cleans up JPEG artefacts. Be clear about what that means, though: it invents detail from patterns it learned, it doesn't recover what the sensor missed. It can sharpen a soft photo convincingly, yet it cannot bring back a face that was never in focus to begin with.
Doing it without uploading anything
There's a quieter benefit to resizing in the browser: your photo never leaves your device. Many 'free online resizer' sites upload your file to a server, process it there, and hand back a download — which means a copy of your image now sits on someone else's machine, subject to their retention policy.
GotConvert does the whole thing locally with the browser's canvas, and for upscaling it downloads a model once (about 5 MB) that then runs entirely on your device. None of your image data is transmitted, so a passport scan, a private screenshot, or a sensitive document stays yours. For anything but the very largest files it's usually faster too, since there's no upload-and-wait round trip.