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How to upscale an image on a Mac
By Himanshu Ranjan · Updated 8 November 2026
To upscale an image on a Mac, select it in Finder and run Resize › Upscale 2× or Resize › Upscale 4× in FileDial. It uses Apple's on-device super resolution, tile by tile, so the picture is not uploaded. It enlarges and sharpens plausibly, but it cannot recover detail the photo never captured.
What upscaling can and cannot do
Enlarging a picture adds pixels but no new information. Wikipedia explains that a smaller image can only carry the information it contains, so any extra detail must be estimated. Classic methods such as bicubic blend neighbouring pixels, which looks smooth but soft.
Learning-based super resolution works differently: it generates a plausible high-resolution image that matches the small one. Wikipedia warns that such tools can invent details that were or were not there. That is useful for a tidy enlargement and unsafe as evidence of what a scene looked like.
Steps in FileDial
FileDial offers two sizes. Resize › Upscale 2× doubles each dimension and Resize › Upscale 4× quadruples them. Both use Apple's on-device super resolution, tile by tile, and the note says transparency is resampled. The result is a new copy beside the original.
- Select the image in Finder.
- Hold the right Option key to open the dial, or right-click and choose Open in FileDial.
- Choose Resize, then release on Resize › Upscale 2× or Resize › Upscale 4×.
- Open the new copy and zoom in to inspect edges, text and faces before you use it.
Pick 2× or 4× sensibly
Bigger is not better. Four times the width and height is sixteen times the pixels, and the more you ask the algorithm to invent, the more likely you are to see odd textures. Try 2× first and use 4× only if you really need the size, such as a small logo or a low-resolution scan that has to print large.
Start from the best source you have. Upscaling a heavily compressed JPG also enlarges its blocky artefacts, so a cleaner original gives a cleaner result. If you have the original file, use that.
- Photos for screens: 2× is usually enough.
- Prints from small images: try 4×, then inspect.
- Pixel art: super resolution may smooth it; classic nearest-neighbour methods keep hard edges.
Logos and flat art
For logos and drawings, a better answer than upscaling may be vectorising. FileDial's Convert › Image to SVG (trace)… writes vector paths traced from the picture, and it works best on logos, drawings and flat art. A vector scales to any size without blur. Wikipedia notes vectorisation suits simple geometric art, not photographs.
Finish with Adjust › Sharpen or Adjust › Reduce noise if the enlarged result needs it, and compress if file size matters.
Check the result honestly
Look at an upscaled image at 100 percent, not zoomed out. Check edges for halos, skin for waxy smoothing, text for invented letter shapes, and patterns such as fabric or foliage for odd repetition. These are the typical signs of a model filling in detail.
Be honest about use. For a family photo you want to print larger, a good upscale is a fine solution. For evidence, a document, or anything where accuracy matters, use the original and say if an image has been enlarged. Wikipedia's warning that such tools can invent details is a good reason not to treat an enlarged image as a record.
If the result is acceptable but soft, follow with Adjust › Sharpen, sparingly. If the original had noise, Adjust › Reduce noise before upscaling can help, because the enlargement otherwise magnifies the noise.
- Inspect at 100 percent.
- Do not use upscaled images as evidence.
- Reduce noise before enlarging.
When upscaling is the wrong answer
If you can find a larger original, use it. If you are making a logo bigger, trace it or ask for the vector. If the image is blurry because of motion or focus, enlarging will not fix it and may exaggerate the blur. Upscaling suits clean but small images, such as old web photos or scans, that you need at a bigger size.
Preview can resize but not add detail: its Adjust Size dialog enlarges by resampling, which looks soft. That is an honest, simple option for modest enlargements. FileDial's model-based upscale is better for larger jumps, and it is slower on large images because it works tile by tile, so try one image before running a whole folder.
A quick decision guide: for a small web photo you need larger, try Upscale 2×. For a tiny image that must print big, try 4× and inspect closely. For a logo, trace it to SVG. For text-heavy scans, consider re-scanning at higher resolution instead. For anything evidential, do not upscale. If the image is also noisy or soft, treat those first, since enlargement magnifies every flaw already in the picture.
Privacy
Many upscalers are web services that need an upload. FileDial uses Apple's on-device model, so the picture never leaves the Mac, and it works with Wi-Fi off.
Questions
Can upscaling add real detail?
No. Wikipedia explains that enlarging adds pixels but no new information, so extra detail is estimated. Super resolution produces a plausible result and can invent details. It is fine for a nicer enlargement, but do not trust it for forensic or evidential use.
Should I use 2× or 4×?
Try 2× first. Four times each dimension is sixteen times the pixels, so the algorithm has to invent much more. Use 4× when you truly need the size, then inspect edges, text and faces at full size before you rely on it.
Is the picture uploaded anywhere?
No. FileDial says Upscale uses Apple's on-device super resolution, tile by tile. It runs locally, files are never uploaded and all tools work with Wi-Fi off. Because the model works tile by tile, large images take longer than small ones, so try one file before a folder.
What is better for logos, upscaling or vectorising?
For logos and flat art, tracing to a vector is often better because it scales to any size without blur. FileDial has Convert › Image to SVG (trace)… for this. For photographs, vectorising does not work well and upscaling is the right tool.