People have lied on the internet for as long as it has existed. That's why Snopes has been around for so many years.

The rise of generative artificial intelligence tools in recent years has meant we at Snopes have spent a lot of time figuring out whether an image shared online was legitimate or whether it was created by AI, a type of image sometimes called a "deepfake." (That word can also be used to describe AI-generated video and audio.)

As generative AI tools have become more advanced, this task has become increasingly difficult, and even experts struggle at times. Determining whether an image is real often comes down to looking at small details for things that are out of the ordinary.

At Snopes, we believe ensuring that images you see online are real is a worthwhile skill to practice, especially given the skyrocketing amount of AI-generated content we encounter online.

Below, we've compiled a list of the most common strategies Snopes reporters have used to figure out whether an image is AI-generated. Beneath each tip, we've also provided an example of an image we debunked using that technique.

These strategies are not foolproof — an image having any one of following characteristics does not immediately mean it's a fake. (Just like that em dash — commonly considered a tell-tale sign of text produced with generative AI — doesn't mean we wrote this with ChatGPT; our writers just like em dashes.)

We recommend using the tips as a checklist instead. The more signs on this list you see in an image, the more likely it is to be AI-generated.

We have one final caveat: As generative models continue to improve, some of these tips and tricks might become obsolete. Multiple new models have pushed the boundaries of realism in AI-generated images, for instance, but some AI companies have introduced a somewhat reliable way to check whether a photo originated from one of those highly realistic models.

The physics of light is incredibly complex, and that means camera mechanisms (our eyes included) are, too. As a result, it's very difficult for generative AI models to accurately depict real light and all of its effects.

The following tips revolve around light effects that Snopes' team has noticed AI models often struggle to get correct.

If the image appears to have been taken during the day, look for shadows (or the lack thereof). If there are shadows, check whether their shape matches what would be expected. Shadows fall in a straight line with the light source that produces them, meaning that shadows of nearby objects should fall in similar directions.