How to spot a fake photo online

“Like many amateur photographers, I do occasionally experiment with editing. I wanted to express my apologies for any confusion the family photograph we shared yesterday caused.”

That was the mea culpa issued by the Princess of Wales after a digitally-altered family photo sparked headlines around the world; a wave of social media speculation; and multiple international picture agencies embarrassing the palace by pulling the image for being "manipulated".

It's not the first time an image by a high-profile individual has been doctored, and it certainly won't be the last. But what signs should people be on the lookout for when trying to determine what they are looking at is fake or not?

Read more: What we know about Kate's photo controversy

Check for any obvious errors

The first thing to do if you think an image is fake is to look for the tell-tale signs it's been doctored.

In the picture taken – and subsequently edited – it's possible to see with the naked eye that the cuff of Princess Charlotte's left hand has been edited. Similarly the pattern of the jumper Louis is wearing has also been changed. There are multiple other smaller potential changes that might be harder to spot (for example, Kate's not wearing a ring and her zip is out of place), but sometimes it's just having a closer inspection that can signal the image is not real.

It's also worth checking whether any individual elements have different lighting or focus. For example, in the image below, Kate's right hand is slightly more blurry than the rest of the image.

If you ever have that thought about an object that doesn't quite fit in an image it might be worth double checking it's not fake.

Reverse image search

If you do have your doubts you can also use reverse image search engines to find other instances of the same photo online.

Google and several other companies like TinEye let you upload an image to their search engine and they will find the closest match they can on the internet. If the search comes back with a near-identical photo except for a few subtle changes then one of the images may have been tampered with.

Some image search engines like Imagedited are specifically tailored to check to see if the photo has been doctored.

Check the metadata

Every digital image contains metadata, tiny bits of info that describe and categorise the photo.

It's a sort of digital fingerprint that can tell you a lot, a legitimate photo will often have a proper file name, the date it was taken as well as information about the camera used to take it. A fake image will often have next to no metadata and will probably have a file name that is irrelevant to the photo.

Metadata is editable so someone who is really looking to deceive an audience may make change it to be more convincing. Social media companies often strip metadata from images for privacy reasons, so check to see if it has been uploaded elsewhere.

According to Sky News, the metadata of the image of Kate was saved in Adobe Photoshop twice on an Apple Mac on Friday and Saturday and the picture was taken on a Canon Camera.

Was it generated by AI?

The growth in artificial intelligence (AI)-generated images can make some of these previous tips redundant, if a robot has made the photo then it is likely the lighting and resolution will be uniform.

However, at the moment AI technology isn't perfect and although there are many different bots making images many of them share a few flaws.

Firstly, AI technology struggles with hands. It doesn't get them wrong every time but when trying to generate fingers in anything other than a relaxed position they often get confused and struggle to make an accurate human hand.

The same is true for jewellery and glasses, AI hasn't quite figured out how they sit on a person just yet.

AI also tends to generate overly smooth surfaces often leading to pictures of people who appear to have perfect skin without any blemishes, dimples or wrinkles – which we all have.

All of these tips can't be applied to every AI-generated image and some of the best are almost impossible to distinguish from real life.

But several companies are building their own tools, including AI technology-based ones, which can determine if an image is real or generated.