How to Replace the Sky in a Photo Online, Free

By Ismail Farooq · 14 November 2026 · 10 min read

To replace the sky in a photo for free, open the Sky Replacer, drop in a photo with sky along the top, choose a blue, sunset, blue-hour, starry or overcast sky (or upload your own sky photo) and click Replace sky. The AI finds the sky in your browser in a few seconds, the photo is never uploaded, and the result downloads at full size. Below is what it did to three real test photos, including the two flaws to check before you post the result.

How do you replace the sky in a photo online?

1. Open the Sky Replacer and drop in your photo. JPEG, PNG, WebP and iPhone HEIC files all open. Pick a photo where the sky reaches the top edge of the frame.
2. Choose the new sky. Blue sky with clouds, Sunset, Blue hour, Starry night, Soft overcast, or A sky photo of my own.
3. Leave “Match the light on the land” on Yes for the built-in skies. It lays a gentle wash of the new sky’s colour over the rest of the photo, so a sunset sky does not sit above grey noon light.
4. Click Replace sky. The first run downloads the depth model once (about 50 MB, or about 27 MB on devices without WebGPU) and keeps it in the browser’s cache; later runs start straight away.
5. Check the result at full size, then download. Look along the horizon and around wires, branches and roof lines (see the edge problems). If it is close but not right, try a different sky: a paler one hides small mistakes better. “Keep editing this result” sends it on to another tool.

The download is a JPEG with the same width and height as your photo. Your original file is not changed.

Which new sky should you choose?

The five built-in skies are painted fresh for each photo at its own size, so they are never blurry from being stretched, and each one comes with its own colour for the “Match the light” wash.

The simple rule photographers use applies here: the light in the sky should agree with the light on the land. If shadows in the photo fall to the left, a sunset glowing on the left looks wrong. If the photo was taken on a grey day with no shadows, a bright blue sky looks a little odd too; brightening the land afterwards with Image Adjust or giving it directional light with the Photo Relighter closes the gap.

How does the tool decide what is sky?

Knowing the rule tells you which photos will work before you try. The Sky Replacer runs Depth Anything V2, an AI model that estimates how far away each part of a photo is (the model and the method are described in the Depth Anything V2 paper; the small model the tool uses is published under the Apache-2.0 licence on Hugging Face). A pixel counts as sky only when all three of these are true:

1. It is the farthest thing in the photo. Depth is relative, so the tool takes the pixels the model rates as the most distant: within 2.5% of the far end of the photo’s depth range.
2. It is bright or blue. Its brightness is above a low threshold, or it is clearly bluer than it is red. This stops a distant dark hill from being taken for sky.
3. It is connected to the top edge. The tool starts from the top row and spreads to every touching pixel that passed the first two tests.

If the area found is less than 3% of the photo, the tool stops with the message “No sky was found along the top of this photo.” Otherwise the area becomes a mask, softened by about one pixel for every 700 pixels of photo width so that leaves and branches blend in, and the new sky is painted into it. You can see the same depth estimate as a picture with the AI Depth Map tool; how to make a depth map from a photo explains how to read one. Where the depth map shows the sky as the darkest, flattest region, the sky replacement will be clean.

Two things follow from the rule. Sky seen through a window, an arch or a gap that does not reach the top edge is left alone. And anything that the model also rates as very far away, bright and joined to the sky, such as a hazy horizon or distant sea, can be replaced along with it.

What happened when we replaced the sky in three real photos?

We ran the live tool on 14 November 2026 in Microsoft Edge on a Windows PC, with three 360 × 492 pixel photos: a lighthouse on a sea cliff, a black and white copy of the same photo, and a narrow street with a tram. We added a fourth file with no sky on purpose.

The pattern is clear. On an open landscape the sky is found cleanly and the tool is quick once the model is cached; the time a run takes depends on your device and the photo’s size, so treat our seconds as an example rather than a promise. A black and white photo needs colour first: run it through the Photo Colorizer, then replace the sky. And the busier the edge between sky and land, the more there is to check.

Why does the horizon move, and where do the haloes come from?

A band of far sea or haze becomes sky

On the lighthouse photo the sea horizon sat about 200 pixels from the top. After every replacement, the new sky reached about 25 pixels lower on the right-hand side, roughly 5% of the photo’s height, so the far strip of sea was painted over and the horizon now slopes slightly. The depth model rates that distant water as just as far away as the sky, and it is bright and blue, so it passes all three tests.

What to do about it:

• Choose a sky that is pale at the bottom. Blue sky and overcast fade to a light colour at the horizon, which makes the change hard to spot at normal viewing size. Sunset and blue hour end in a strong orange glow that shows it clearly.
• Crop after replacing if the horizon line is near an edge of the frame you do not need, with the Image Cropper.
• Use an editor with an edge slider when a dead-straight sea horizon is the point of the photo. Photoshop’s Edit > Sky Replacement has Shift Edge and Fade Edge sliders for exactly this, as Shotkit’s walkthrough shows. The Sky Replacer has no edge control.

A pale outline around wires, twigs and roof lines

On the street photo the tram wires kept a white outline and the roof edges a pale rim. The depth model estimates distance in soft patches rather than to the exact pixel, so the sky right next to a roof, or around a wire one or two pixels wide, is rated slightly nearer than open sky and fails the “farthest” test; those pixels keep the old sky. Photos longer than 1,024 pixels are measured on a smaller copy, and the mask is then scaled up and softened. The softening is deliberate: a hard edge would look cut out with scissors.

• The halo is the colour of the old sky. It nearly disappears when the new sky is similar in brightness: replacing a pale blue sky with Blue sky with clouds hides it; replacing it with Starry night shows it most.
• Photos with only a few wires can be cleaned first: remove the wires with the Object Eraser, then replace the sky.
• Bare winter trees against the sky are the hardest case for every sky tool, not only this one. Expect the gaps between fine branches to keep some of the old sky.

How do you use your own sky photo?

1. Choose A sky photo of my own under New sky. A Sky photo box appears.
2. Add a photo of sky only, taken in landscape shape. The tool crops it from the centre to cover the top of your photo down to the lowest point the old sky reached, and at least the top 30% of the frame.
3. Click Replace sky and check the light. “Match the light on the land” has no colour to add for an uploaded sky, so the land keeps its own colour; warm or cool it afterwards with Image Adjust if it does not match.

The best sky photos are your own from the same place and the same time of day: the sun is on the same side and the haze at the horizon matches. A sky with the sun in it does not work well unless the land in your photo is lit from that side. Use a sky picture you took or are allowed to use; a sky downloaded from a search engine is usually someone else’s photo.

Should you use a browser tool, another online tool or Photoshop?

Other free online sky tools usually work on a server. That is not wrong, but read their limits: Upsampler, for example, states on its page that output is about one megapixel and that free use has a daily allowance, and Magic Eraser says its free use is limited per day and that you cannot pick the sky. The Sky Replacer has none of these limits, and the trade-off is that the first run downloads the model to your device.

When is replacing a sky not honest?

A new sky is a creative edit, and most of the time nobody minds. It becomes a problem when the photo is presented as a record of something:

• Property listings. In California, AB 723 has required since January 1, 2026 that an altered advertising image carry a statement saying so, with access to the original, and a replaced sky is an altered element. Label it “Sky digitally enhanced” and never use it to hide a pylon, a mast or a building. The real estate photo editing guide covers the rules and wording in detail.
• News, evidence and contests. Many photo competitions and every newsroom forbid replacing parts of the scene. Read the rules first.
• Travel and hotel reviews. A blue sky over a rainy-season photo misleads the next visitor.

Keep the original file in every case, so you can show what the camera recorded.

Troubleshooting

The free AI image editing guide lists every other AI tool on the site that runs on your device the same way.

Questions