Reverse image search: What are they, and how do they work?

• If you want to add images to your blog or sales material, unless you make your own, you'll need to find some stock images.
• But how can you be sure you have permission to use them?
• Well, that is where conducting some reverse image searching pays dividends.

Adding images to an online blog or a piece of sales material is an excellent way of making it look more presentable and exciting. But if you aren't good at taking relevant pictures or don't have a lot of pictures, you'll usually get them from the internet.

While that sounds obvious enough, unless you know the original creator and have their permission to use it, you could be exposing yourself to potential copyright claims in the future. Even using "copyright-free" images from sites like Flickr isn't always foolproof, as creators can claim other people's work as their own.

So, how do you navigate this minefield safely? One option is using images in the public domain, but you are often stuck with low-quality or irrelevant images. But there is another way, something called reverse image searches.

But what is it? And how do you do that? Let's find out.

What is a reverse image search?

As the name suggests, a reverse image search is a technique for querying the internet for an image to see if any other exact examples are present. More technically, a reverse image search is a content-based image retrieval (CBIR) query method that gives the CBIR system a sample image it will use to base its search.

In particular, reverse image search is defined by the fact that it doesn't have any search terms. This means that a user doesn't have to guess at keywords or terms that might or might not bring up the right results.

A reverse image search lets users find content related to a specific sample image, find out how popular an image is, and find altered versions of the image and works based on it.

There are a few products out there you can use to perform this sort of search, but Google’s reverse image function is one of the most popular.

More accurately called 'Google Images' or 'Google Search by Images', the function had existed since 2011 when the internet giant began to offer it. This function is most useful for specific users for various reasons.

For example, you can use it to check for the original owner of an image to verify or check for any potential copyright issues using it. It can also help confirm or fact-check a particular image used in a news report, meme, etc.

Great, so how do you do it?

There are a few ways to use it, as it happens.

But, in any case, you’ll first need to navigate to Google Images and select the camera symbol from the search results. From there, you can post a link to an online image or upload an image from your computer.

For the latter, you need to right-click the image and choose “Copy Image Address” to paste a link to an internet image. The search box can then be used to paste this into, and the default setting for this should be Paste Image URL.

For the former, you can drag a file from your computer into the search bar using Chrome or another browser like Firefox.

If you use Google’s Chrome, however, you get the added benefit of running a reverse image search anytime you encounter an image on a website. To do this, right-click the image and choose Search Google for Image.

The search results generated do vary from the typical Google searches you are used to, but they are easy to understand.

Typically, when looking for photographs on Google Images, you type in a term like "flowers" or "landscape," and Google tries to show you the images that are most closely connected to that term.

But when you use reverse image search, you first upload an image or type in the URL of an image on the web. Giving Google a clear idea of what you're looking for lets it finds images and information that are particularly relevant to that image.

Great, but how does this seemingly magical tool work?

How does reverse image search work?

Well, it's not magic, as you've probably guessed. Reverse image searching, irrespective of which service you use, each search engine's reverse image search works a little differently, and they don't share their exact algorithms.

Still, the basic ideas are out there and easy to understand, and tend to work on a few basic concepts. These are as follows.

The first is something called fingerprinting.

As the term suggests, each image has specific characteristics similar to the fact that no two fingerprints are alike (usually).

Pictures may be more unique than fingerprints because it is almost impossible for two images to have the same arrangement of pixels. In contrast, the chance of two fingerprints having the same structure is around 1 in 64 billion, which is practically impossible to duplicate naturally.

But how, you might wonder, how can a picture be fingerprinted? Well, that depends entirely on the algorithm.

The steps used to determine an image's unique arrangement of pixels tend to be different, but most follow the same basic pattern.

First, each algorithm needs to measure the image's features, including color, texture, gradients, shapes, relationships between different picture parts, and elements like Fourier transforms.

Fourier transforms, if you are unfamiliar with the term, is a mathematical operation that breaks down functions into their frequency components. We won't go deeper into this concept as it is a little off-topic. Still, this sophisticated process generates a characteristic pattern that can be used to distinguish data sets.

Even if an image has been resized, blurred, rotated, or changed in some other way, an algorithm, if sophisticated enough, can try to find hits by using the above and other features.

Pretty impressive when you think about it.

Another component tends to relate to image encoding, storage, and searches.

Every part of an image can be turned into a string of letters and numbers that are easy to store and look up in a database. Whatever features are taken from the picture and saved will be the entry for that picture in the reverse image search engine.

At the time of writing, TinEye's database (more on them later) has stored around 56.3 billion indexed images. This means that they've run their algorithm over many pictures and kept all of the 'fingerprints' so they can compare searched images to them.

This provides a valuable resource to speed up reverse image searching if the image search results have already been run in the past. This is akin to cookies, or other stored data, from search engines like Google Chrome that exist o help speed up your surfing experience.

Once the above has been determined, the next step is determining which images a submitted image file correlates with.

When you upload a picture, it will go through the fingerprinting algorithm of the reverse image search engine. The search engine will then try to find the entries with the closest fingerprints.

This is called "image distance," and each search engine chooses which factors to compare and how much weight to give them. However, they all try to find a total image distance that is as close to zero as possible.

If an image matches precisely, this is considered a hit, and the relevant information is displayed to the user. If no matches are found, the image has been materially changing enough to defeat the algorithm or is, for all intents a purposes, a unique image.

Why do people use reverse image search?

So why would you use reverse image searches in the first place? Well, like anything in life, your reasons may vary widely. Still, in most cases, users attempt to find where an image was first posted on the internet (for whatever reason, for example, this may indicate who holds the copyright).

Beyond that, there are a few more technical reasons people might want to do this…

1. Reverse image searching is excellent for authenticating images

Whenever you see a generic image on a website or perhaps attached to an email, you don’t know how old it is or where it came from. While it may include a timestamp on the image or in its metadata, the former can be forged using an image editor, and the latter only tells you when an image file was created.

This sometimes makes it tricky to verify an image's authenticity and can prove to be a minefield if you want to check who owns the actual copyright to an image you may want to use. Suppose you're going to use an image for personal use. In that case, this isn’t necessarily a problem, but if you run a blog or want to make some promotional material that includes some nice graphics, not knowing the original content creator could leave you open to copyright claims.

It is also hard to determine if an image has been doctored or changed (for whatever reason), which is particularly problematic if it is used to support some claim. Examples could include screenshots of data, graphs, or other photographic “proof” of something.

In an age of resources like Photoshop, this can be a real headache to disentangle without spending hours searching the internet to find the source. You also can't always trust websites that say their images are "copyright-free" and can be used without worry.

Sometimes, perhaps more often than not, users on these platforms may claim the copyright to an image they don’t own. While you might then use it in good faith, the actual copyright owner could raise a claim against you and the user in question.

So, this is an area where a reverse image search tool comes into its own.

But, they are not foolproof.

Most of the time, reverse image searches bring up a lot of images that look the same at first glance but are different. Sometimes a face has been switched, or something has been taken out of or added to the photo. Don't think this doesn't happen. There are websites whose sole purpose is to change pictures, usually for funny or political reasons.

Sometimes, pictures have been flipped (laterally reversed). This is an option to try when reverse image searches yield different results.

Reverse image searching is now essential for mainstream publications, especially news organizations. Now that you can do it in a few seconds, it makes sense to do it even for less critical things.

2. Reverse Image searching is great for tracking images over time

If you have a website, print brochures or press releases, or put copyright-protected photos online, you can be sure that your pictures will be used again. A reverse image search tells you where and when the picture was taken. After that, you can decide if a second use is legal and appropriate and what to do next.

You can find out how popular your press release or blog post was by searching for publicity and advertising images. You may also find coverage that text searches need to include, perhaps in other languages.

You may also find that your pictures are used in ways you don't like, like showing how products from a competitor work. If so, you can ensure they are labeled and credited correctly. Remember that you can't complain about pictures you don't own.

Some websites may link to an image on your site instead of their own, using your bandwidth. This is not only annoying but consumes some of your valuable internet data resources.

You might also find copyright-protected photos that you still need permission to use. You can ask them to take them down or send them a bill.

In either case, reverse image search can help you find a lot of helpful information that would be hard to find any other way.

3. Reverse image searching can help you verify someone’s identity

From an online security point of view, reverse image searches are an invaluable tool for checking a third person's identity. This is especially true for investigating profile images on social media sites like Twitter, Facebook, or LinkedIn.

Using someone else's image, or a stock image, is a favored tactic of hackers and potential scammers, so the ability to check the origin of an image is precious. For those who hope to find potential dates online, or if you want to protect your children online, you should consider using a reverse image searching tool if you are ever in doubt about the identity of someone you are communicating with.

You never know; it may save you a small fortune from being scammed or even save someone's life!

Can you only use Google to perform a reverse image search?

As we already said, there are other ways to do this than Google's reverse image search. There are, for example, a series of plugins and other websites that do the same thing or something similar.

Let’s take a look at some examples.

1. TinEye is an excellent alternative to Google’s reverse image search

One example we have already mentioned is a tool called TinEye.

Idée, Inc., a company based in Toronto, Ontario, Canada, makes a tool called TinEye that lets you search for images in reverse. It differs from Google’s tool because it was the first image search engine on the web to use image identification technology instead of keywords, metadata, or watermarks.

Like Google’s function, you can upload an image, and TinEye makes a "unique and compact digital signature or fingerprint" of it and matches it with other images that have already been indexed. This procedure can compare even heavily edited versions of the image you send, but it won't usually show you images that look similar to the one you sent.

You can also add TinEye's Chrome extension, which gives you a quick way to look up historical information about an image. Once installed and activated, you can right-click on an image of interest, select the TinEye tool, and let it work its magic.

TinEye is one of the most useful reverse image searching tools, and for a good reason. Its proprietary MatchEngine API enables its free reverse image search feature.

By offering the service for free, they are continuously feeding MatchEngine with fresh content to improve and become smarter at image matching. Then, for a fee, TinEye makes its full-featured API available to businesses or researchers interested in using it for more extensive projects.

They give you access to their system via some straightforward API connectors so you can easily spot duplicate or edited photographs, compare your collection of images to others, or take other actions to ensure your image library is managed and compliant in the manner you need.

Pretty neat.

2. Bing has a reverse image search tool too

First unveiled by Microsoft in 2014, the Bing Visual Search tool is an excellent alternative to TinEye or Google's reverse image searcher. It is easy to use and works in most other browsers too.

To use it, navigate over Bing's tool and then: -

• Upload an image from your computer, or copy the URL and paste it into the space provided.
• Then, let it do its magic.

Once the image is uploaded to the search bar, the Bing Visual Search tool will conduct a search based on its algorithm and then display the search results it generates. This will typically present data and other information about: -

• The website(s) where the picture is currently used.
• Examples of similar images it has found.
• Show you related queries to yours.

In 2016, Bing did come out with a mobile app, but it can only be used on Apple devices.

3. Did you know Pinterest has a reverse image searcher?

Believe it or not, even Pinterest has its own reverse image searching tool. Referred to as its "crazy-fun image search tool," it was first unveiled in 2015 and quickly became a popular resource.

The Pinterest Visual Search Tool is a must-try for marketers who fall in love with an image they find while browsing Pinterest but don't know where it came from or what it's called. But, for those who are not too familiar with Pinterest, it is still a valuable tool to consider using too.

To use it, navigate to the relevant section of the Pinterest app, and then: -

• Click the search box in the upper right corner.
• Choose the picture pin you want to look for.

Pinterest will then show you pins where the image is used and similar pins with images very similar, or identical, to the one you chose.

You can also sort your visual search results by topic to help you find exactly what you're looking for. You can also zoom in on an image or search for a specific part of it.

Interesting, but if you are familiar with Pinterest, you may wonder how it differs from Pinterest Lens.

Pinterest Lens is a feature that lets you take a picture of something in the real world and then look for it on Pinterest. It does this by using "image detection" to figure out what it is.

In theory, this is different from a reverse image search because it looks for the same item in places where it can be bought rather than just using an algorithm to find the same or similar images already on the web.

4. PREPOSTSEO is another convenient reverse image-searching tool

Another great reverse image searching tool is something called PREPOSTSEO. Designed more for marketers and content producers, the team behind it also offers other features and tools that include a word counter and a plagiarism detector.

Although PREPOSTSEO is free, there are paid premium plans that may be handy for marketers and content producers who want a single solution to handle all of their needs.

Using PREPOSTSEO, reverse image search is straightforward, and users have three main options for conducting a reverse image search: -

• From your computer or mobile device, upload a picture to the software.
• The image URL can be copied and pasted into the search area.
• Click "Search Images" after seeing an icon for your image.

Your reverse image search results will then be categorized by PREPOSTSEO using the search engine's criteria. The program, for instance, will classify results from Google, Bing, and Yandex.

Users select the "Show Matches" button for each category to display the results. You can then view all the related search results for your image and the keyword associated with that specific image in a new tab.

5. Reverse Image Search is another powerful reverse image-searching tool

Another useful reverse image searching tool is a site called Reverse Image Search. Self-described as a "super-fast image finder," this no-frills reverse image searching tool is an excellent alternative to Google and others listed above.

According to Reverse Image Search, their tool is powered by cutting-edge artificial intelligence algorithms. It compared the uploaded images to the images in the database and indexed URLs.

This picture finder also checks the likeness of the items, forms, color schemes, and other components. Additionally, sophisticated algorithms include facial recognition tools that are now functional for images of celebrities. It compares the facial characteristics to every photograph on the database and the internet.

Using the tool is very similar to other tools described above too.

• First, you navigate to its homepage.
• From there, you upload an image, paste an image's URL, choose a keyword, or upload an image from Google Drive or Dropbox.
• You can select a particular search engine and hit "Search Images."

You can also "Check Images" using this tool to find images with selected image search engines online.

6. Revesee is another great reverse image-searching app for your iPhone or iPad

If you have an iPad or iPhone, and the above aren't available, some third-party iOS apps are also available. One good example is Reversee, which is one of the most popular. It is easy to use and free, which makes it a good choice.

To use it, first install the Reversee app on your iPhone or iPad by downloading and installing it, then opening it.

When you open the app, you can do a few things, like using the last photo you used or copying and pasting from somewhere else. Choose a photo by tapping "Choose a Picture."

Once you pick an image, Reversee then gives you a few options to choose from. You can, for example, crop the image, change the size, or choose search engines.

To do these things, tap on the icons at the bottom.

If you don't want to change your photo, tap "Search" at the top right of the screen when you're done. The results will then start appearing and should be easy enough to decipher.

How do you reverse image search from your phone?

Reverse image searching is pretty straightforward using a desktop computer, but did you know you can perform a similar function from your smartphone? If your phone runs on Android, it should also have a restricted version of its reverse image search functionality.

To access it, open images.google.com in a web browser on your mobile device. Chrome works best, but you should be able to perform the same functions through other browsers like Safari, Firefox or DuckDuckGo, etc.

Once on the site, tick the box for "Desktop site" from the list of options that appears after tapping the three dots in Chrome. That will force the website to load the desktop version of the Google Images webpage instead of the slimmed-down mobile variant.

For Safari, the process is slightly different, however. Click on the Aa symbol on the left of the search box to access a similar function called "Request Desktop Website."

You'll know it's worked because the landing page should change to a shrunk-down version of a desktop Google homepage (your browser is trying to cram the much larger desktop page onto your mobile screen). Mobile versions of webpages are usually redesigned to fit the much smaller screen of mobile phones.

You should also see a camera symbol appearing on the page. Your camera roll can then be used to upload images.

Chrome also enables a solution for reverse image search, depending on your phone. Hold your finger on the image in your browser that you want to search until a pop-up menu displays, then select Search Google for This Image from the menu that appears.

If this doesn't work for whatever reason, you can also choose "Open Image in New Tab." Once copied, return to images.google.com and paste the URL there.

Reverse image search results for either approach then show up; you might need to click the More sizes option at the top to see only the photos. You'll notice options to focus your search, like finding animated GIFs, clip-art alternatives, or searching by the original image's color scheme.

On Android, you also have the option to use Google Lens too. It even comes with a standalone app too. However, while Google Lens can be used to reverse image search, it is more about assisting you with activities than finding a source image, such as rapid translation, object identification, or buying a product.

That said, it may glean some information you can use to verify the image's authenticity or its source.

And that's your lot for today.

Reverse image searching is a powerful way to find the source of an image you may want to use on your blog or check on someone's profile image. If you are an image creator, it is also a handy tool to see who, if anyone, is using it without your permission.

Doing so will protect you from getting hit with copyright claims and save you from being defrauded by someone claiming to be who they are not. For these reasons, you might consider adding reverse image searching to your toolbox.