How to Blur the Background of a Photo With AI

To blur the background of a photo, you keep the subject sharp and soften everything behind it, the way a camera with a wide-open lens would. You don't need to have shot it that way: an AI editor can find the subject in a finished photo and add the blur afterwards. In SmileToAI's AI Image Generator there are two ways to do it, both in the image editor:

• Blur background (a preset, one click). The editor adds a realistic, shallow depth-of-field blur and keeps the main subject sharp. It gave a soft, natural blur in our test. There is no strength slider.
• Prompt Edit (a sentence you write). You say how strong the blur should be and what must stay sharp. Our prompt for a strong blur came back clearly blurrier than the preset.

The short version, step by step:

1. Upload your photo to the AI Image Generator and open it with Edit image (the pencil icon).
2. For a soft blur, open Presets and choose Blur background. For a stronger one, open Prompt Edit and describe the blur (the exact prompt we used is in Step 3).
3. Select Run 1 Edit and wait for the new version.
4. Set the version you like as the cover and Download it.

Both routes keep your original photo and save the result as a new version. Is it free? Not per run: both are AI edits paid in Sparks, SmileToAI's credits. But a free account comes with 5,000 Sparks a month, and each of our runs used 250, so the Free plan covers about 20 blurs a month without paying. Each run came back in under half a minute.

We ran both on the same photo of a ginger cat on a garden bench, with a brick wall, roses and a fence behind it, all in sharp focus. Here are the three versions, exactly as they came back:

Left, the original photo. Middle, the Blur background preset (250 Sparks). Right, a Prompt Edit asking for a strong blur (250 Sparks). No retouching and no second tries.

What you'll need

• A photo with a clear subject in front of a background: a pet, a person, a product on a table. JPG, PNG and WebP all work.
• A SmileToAI account. The Free plan's 5,000 monthly Sparks cover many runs at the cost we saw.
• A browser, or the SmileToAI app on iOS or Android, which has the same presets and Prompt Edit.

The photo in this guide is SmileToAI's own: we made it with the AI Image Generator and asked for everything to be in sharp focus, front to back, so the blur would have something to work on. It is 1024×1024 pixels. Because we generated it, it went straight into the gallery; with your own photo, upload it first as below.

Step 1: Upload your photo and open the editor

1. Open the AI Image Generator and start a session (New session in the sidebar).
2. Open the generation settings (the sliders button in the composer) and choose All settings. Under References, select the plus button (Pick from library), then Upload images, and pick your photo.
3. In the References list, select Add reference to gallery next to your photo. It now sits in the gallery as an image you can edit.
4. Hover over the image in the gallery and select Edit image (the pencil icon).

The editor opens with the photo on the left, the Version Map on the right, and the editing tabs along the bottom: Crop/Reframe, Presets, Prompt Edit, Expand, Quality and Export.

Step 2: Run the Blur background preset

1. Open the Presets tab.
2. Select Blur background. It is marked Optional mask.
3. Leave No mask selected to let the editor find the subject and the background on its own.
4. Select Run 1 Edit. The arrow next to it sets how many variations to run: 1, 2, 4, 8 or 16.

The Presets tab with Blur background selected and no mask. Replace background and Relight sit in the same grid.

The preset asks the model for "a realistic shallow depth-of-field background blur" that keeps the main subject sharp, cleanly separated and naturally lit. Our run came back in under half a minute and used 250 Sparks. The new version appears in the Version Map under the original, labelled with the preset's name:

The preset's result in the editor. The original stays at the top of the Version Map; the blurred version hangs under it.

What changed: the brick wall, the roses and the fence went soft, as if shot with a moderately open lens. The cat's fur, whiskers and eyes stayed sharp, and so did the bench it sits on. The watering can next to the cat stayed fairly sharp too: the model treated it as part of the foreground, which is what a real lens would do at that distance. The result is subtle. If you want the background to melt away, use Prompt Edit.

Step 3: Get a stronger blur with Prompt Edit

The preset has no strength setting, so for a heavier blur you describe it yourself.

1. In the Version Map, select the version to edit. We picked the original again, so the second result is a fresh take rather than a blur on top of a blur.
2. Open the Prompt Edit tab.
3. In Edit prompt, say how strong the blur should be and what must stay sharp.
4. Select Run 1 Edit.

This is the prompt we used, word for word:

Blur the background strongly, like a portrait photo taken with a wide-open lens: the brick wall, roses, fence and watering can become a soft, creamy blur. Keep the cat and the bench it sits on sharp and unchanged: same pose, fur, markings, eyes and whiskers.

The Prompt Edit tab with the blur written out. Improve prompt and Suggest edits can help when you are stuck for words.

It came back in under half a minute and also used 250 Sparks. The difference shows best up close. Here is the same corner of the fence and roses, top right of the photo, in all three versions at full size:

A 400×400-pixel corner of each version. Left, the original. Middle, the preset. Right, Prompt Edit. The fence boards are still readable after the preset and only soft stripes after the prompt.

The cat kept its pose, markings, eyes and whiskers in both results. Ask for what you want kept as plainly as what you want blurred: listing "pose, fur, markings, eyes and whiskers" is what held the cat steady.

A few prompt habits that helped:

• Name the strength in photographers' words. "Strongly", "soft, creamy blur" and "a wide-open lens" all point the model the same way.
• Name what should blur, not just "the background". Listing the wall, roses, fence and watering can told the model where the background starts.
• Name what stays sharp. The subject, and anything it touches (here, the bench), so the blur doesn't creep onto it.

For more wording that works on photo edits, see our tested AI photo editing prompts.

Step 4: Compare, set a cover and download

Every run is saved as a new version of the image, so the original is never overwritten. The Version Map shows the whole family: the original at the top, and each edit linked under the version it came from.

1. Select a version in the Version Map. Compare to parent and Compare to root compare it with the image it came from or with the original.
2. Select Set as cover on the version you want. The gallery then shows that version for the image.
3. Close the editor and use Download on the image in the gallery.

Both results came back at 1024×1024 pixels, the same size as the original. Then put the file where it is going: a profile picture, a product listing, a social post.

Common problems and fixes

Part of the subject went soft. The model decides what counts as the subject, so a tail, a hand or the edge of a product can get blurred with the background. Mask the background with Box or Brush under Mask tools (Scribble in the app) so the edit is limited to it: for Blur background, the mask marks the area to blur, not the subject to keep. Or list the part in your prompt as something to keep sharp.

Something in the background stayed sharp. Objects close to the subject, like our watering can, can be read as foreground. Name them in a Prompt Edit as things to blur, as we did, or cover them with the mask.

The blur is too weak or too strong. The preset has one setting. Use Prompt Edit and say "slightly", "strongly" or "a soft, creamy blur", then run two or four variations and keep the closest.

The subject changed a little. The model redraws the image, so small details can drift. Say what must not change (pose, colour, markings, logo, text), and compare the result with the original using Compare to root before you download.

You want a different background, not a blurred one. Use Replace background in the same Presets tab, or describe a new scene in Prompt Edit; our guide on changing the background of a photo shows both. If you only need the subject cut out on a transparent background, see how to make a background transparent.

Which route should you use?

Use the Blur background preset when you want a natural, subtle blur in one click: it softened our wall and roses without touching the cat. Use Prompt Edit when the background should melt away, or when you need to say exactly what blurs and what stays sharp: you write the strength, and you get it, at the same cost. Both sit in the same editor, both save a new version instead of overwriting your photo, and in our test each cost 250 Sparks of the Free plan's 5,000 a month.