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For a crisp, all-or-nothing shape, use a clip path: Canvas clip() if you are already drawing into a canvas, or CSS clip-path/SVG <clipPath> if the image should remain an HTML or SVG element. Use a mask when the edge needs a fade, translucency, or grayscale control. Neither approach is universally faster; performance depends on the browser and workload.
What is the difference between a clip path and a mask?
A clip path defines a region: content inside it is visible, and content outside it is hidden. It creates a hard silhouette, apart from antialiasing at the edge. A mask assigns visibility across the image, so pixels can be fully visible, fully hidden, or partially visible. That makes masks appropriate for soft fades and translucent artwork as well as hard-looking shapes.
The distinction is much like cutting a shape from paper versus placing a semitransparent stencil over it. The SVG 1.1 Recommendation describes clipping as a hard mask and masking as capable of graduated transparency: W3C SVG 1.1: Masking.
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| Need | Choose | Why |
|---|---|---|
| Circle, polygon, star, or another crisp cutout | Clip path | It expresses a simple inside/outside silhouette. |
| The image is already being drawn into a canvas | Canvas clip() |
The clipping region limits subsequent canvas drawing. |
| The image should remain a normal page element | CSS clip-path or SVG <clipPath> |
The effect can be applied to HTML content without drawing it into canvas. |
| Soft edge, fade, translucency, or grayscale-driven visibility | CSS or SVG mask | A mask can represent partial visibility, not just inside or outside. |
| Generated pixels or an existing canvas rendering pipeline | Canvas clipping | It fits a workflow that produces its image through canvas drawing. |
MDN notes that clipping can perform better when a basic shape is all that is needed and can be easier to interpolate. This is qualitative guidance, not a universal benchmark; profile the actual page and supported browsers before making a performance decision. See MDN: CSS clip-path.
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How Canvas clipping works
Canvas clip() restricts subsequent drawing to the current path or a supplied Path2D. Each new clip intersects with the existing clipping region, so content must fit inside every active clip. Clipping changes the canvas drawing state; scope it with save() and restore() so it does not unintentionally affect later drawing.
ctx.save();
ctx.beginPath();
ctx.arc(100, 100, 80, 0, Math.PI * 2);
ctx.clip();
ctx.drawImage(image, 20, 20, 160, 160);
ctx.restore();Here, the image is drawn only inside the circular path. A common mistake is to call fillRect() and expect that rectangle to become the clipping path: it does not. Build the geometry as a path—for example with rect()—before calling clip(). Canvas supports the nonzero fill rule by default and also accepts evenodd. Consult MDN: CanvasRenderingContext2D.clip().
How clipping and masking work on HTML elements
If the image should remain an <img> in the document, CSS clip-path can apply a basic shape or reference an SVG <clipPath>. SVG effects can also be referenced from CSS on HTML elements. Clipping may affect the clickable area too, so check pointer interactions when a clipped link or control overlaps nearby content. MDN explains these options in its SVG <clipPath> reference and guide to applying SVG effects to HTML.
For a mask, CSS mask-image accepts an image or gradient source, including an SVG <mask>. The mask’s alpha or luminance determines how much of the element is visible. With mask-mode: match-source, ordinary image masks generally use alpha, while an SVG <mask> defaults to luminance unless configured for alpha. A black-and-white SVG that looks opaque can therefore behave differently from what you expect if its luminance is driving visibility. See MDN: CSS mask-image.
Fix common masking and clipping problems
The masked image is completely invisible
Check that the mask URL is correct, the resource has loaded, the element has nonzero dimensions, and the format and origin are supported. MDN states that an empty, failed, missing, or unsupported mask image is treated as transparent black, which reveals nothing. Also verify whether the mask uses alpha or luminance; the wrong interpretation can make the result unexpectedly faint or invisible.
The mask is tiled or misaligned
Review mask-repeat, mask-size, and mask-position. Their values control whether and how the mask repeats, scales, and aligns with the element.
The Canvas clip affects later drawings
Put the clipped drawing between save() and restore(). Remember that clips intersect: a later clip narrows the existing region rather than replacing it.
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When referencing external SVG effects from CSS, use an SVG on the same origin as the HTML document, as MDN advises.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check browser support for the features you use
MDN describes Canvas clip() as widely available and established across browsers since July 2015. Its mask-image reference describes the feature as widely available since December 2023, while noting that support for some parts varies. Check the compatibility details for the specific mask features and browser versions in your target audience before relying on them.
For performance, compare the actual implementation in the browsers and rendering workload you support. There is no universal Canvas-versus-DOM/SVG winner established here; the right choice follows the desired visual effect and rendering pipeline.
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