What Does JPEG Stand For? The Complete Guide to the Image Format You Use Every Day

by Lina Thorne • Updated 8/1/2025 · Posted in Photography

Have you ever downloaded an image from the Internet, uploaded a photo to social media, or taken a picture on your smartphone? If the answer is yes, there’s a high chance you’ve come across a JPEG file. In fact, you probably use JPEGs every day.

It might come as a shock, but around 74% of all images on the Internet are in JPEG. More to that, even older browsers and devices won’t have any issues displaying a JPEG image, which isn’t the case for newer formats like HEIC or WebP.

JPEG is everywhere. But do you actually know what JPEG stands for?

Learning more about this popular image format can actually be pretty beneficial. For instance, you’ll know exactly how to keep the file size of your image small without sacrificing too much quality.

Luckily, our comprehensive guide covers everything you need to know about the JPEG format, including:

The definition of JPEG and whether it’s different from JPG
How JPEG compression works
The history of JPEG
Key advantages and disadvantages
When to use and avoid JPEG
What you can do with JPEGs using Watermarkly’s online tools.

Let’s get started!

What Does JPEG Stand For?

JPEG stands for the Joint Photographic Experts Group, which is the name of the committee that developed the standard in the late 1980s and published it in 1992. The term “JPEG” can refer to both the compression algorithm and the file format that uses that algorithm.

JPEG is a lossy format. It simply means that it uses lossy compression. What is lossy compression, you may ask? Well, it’s the type of compression that can drastically reduce the file size by permanently removing some redundant data that the human eye barely notices.

JPEG vs JPG: What’s the Difference?

You might have seen both .jpg and .jpeg file extensions. Some people think that they are two different formats, but they actually aren’t.

The thing is, early versions of Windows only allowed three-letter extensions (hence.jpg), while macOS and UNIX always supported longer extensions (.jpeg).

Today, both extensions work the same way, and modern operating systems recognize them interchangeably.

How Does JPEG Compression Work?

JPEG uses a complex mathematical process called the Discrete Cosine Transform (DCT) to compress images efficiently. Here’s a simplified breakdown:

Color Space Conversion. The human eye is far more sensitive to luminance (brightness) than chrominance (color). JPEG exploits this by converting RGB data into the YCbCr color space, where Y represents brightness, and Cb/Cr carry color information.
Downsampling (Chroma Subsampling). Then, chroma channels are heavily downsampled (often using 4:2:0 ratio), reducing color resolution without noticeable quality loss.
Discrete Cosine Transform (DCT). The image is divided into 8x8 pixel blocks. Each block undergoes DCT to separate low-frequency (smooth areas and general shapes) from high-frequency data (textures and edges).
Quantization. Next, the DCT coefficients are divided by a quantization table. This means that high-frequency components get rounded off or discarded, while low-frequency components are preserved. Since the human eye doesn’t detect loss of color and details in busy and textured areas, the algorithm can remove more data from these areas.
Entropy Encoding (Huffman Coding). Finally, the data is compressed using Huffman coding to make the file size smaller.

The DCT process does sacrifice some image fidelity, but it often does so without a noticeable loss of quality, especially if you don’t zoom closely into the image.

In addition to all of this, there are also two main encoding methods in JPEGs – baseline and progressive.

Baseline JPEGs are encoded and decoded sequentially, line by line. Each line is fully rendered before the next one is displayed.

Meanwhile, progressive JPEGs are divided into multiple scans. The first scan shows a blurry version of the entire image. The image quality gradually increases with subsequent scans.

To put it simply:

Baseline JPEG loads from top to bottom. The entire image is visible only when the last line is fully rendered.
Progressive JPEG loads in multiple passes. You see the entire image in low resolution right away, then its quality gets better.

A Brief History of the JPEG Format

The story of the JPEG format begins in the late 1980s, when the Joint Photographic Experts Group was formed to design a compression method that could reduce image file size while preserving decent image quality. The group consisted of experts from the ISO (International Organization for Standardization) and the CCITT (International Telegraph and Telephone Consultative Committee).

After years of research, testing, and refinement, the JPEG standard was officially published in 1992.

JPEG came into existence quite timely – digital photography was emerging, and the internet was beginning to expand beyond academic and governmental use. The format quickly became the top choice for storing and transferring images, especially when the bandwidth or storage were limited, which was often the case with the dial-up Internet.

Before JPEG, images were often stored as bitmaps or in lossless formats, and as a result, their file sizes were impractically large.

Advantages of JPEG

Excellent Size-to-Quality Ratio. The main reason why JPEG has become so popular and remains popular is its ability to strike a great balance between small file size and good image quality. Thanks to this, you can easily store and share high-resolution images without any issues.
Universal Compatibility. No matter what device you’re using – be it a Windows PC, a Mac, a smartphone, or even an old digital photo frame – it probably can open a JPEG. This format can also be edited by virtually any photo app: from basic tools like Paint or Preview to professional software like Adobe Photoshop or Lightroom. Since 1992, some new image formats have been created. For instance, WebP, AVIF, and HEIC. In some ways, they are more efficient than JPEG. However, none of them is as widely supported as JPEG.
Fast Loading. This lossy format is a perfect choice for images you want to share online since it produces files of a smaller size. As a result, your visual content will load quickly on a web page. So, whenever fast loading speed matters, go for JPEG.
Perfect for Photographs. JPEG handles images with lots of colors, gradients and fine details like photographs particularly well. Skin tones, landscapes, and everyday scenes are rendered with enough clarity and detail that most users don’t notice any quality loss.
Metadata Support. JPEG files can store EXIF metadata such as camera settings, date and time, shutter speed, GPS location, and more. This information is usually extremely important for photographers and archivists.

Disadvantages of JPEG

Permanent loss of data. The downside of lossy compression is that you won’t be able to restore the compressed file to its initial state. Additionally, every time you save a JPEG, especially after editing, it loses a bit more quality. As a result, visible artifacts like blurring or blockiness may appear in your image.
Not Great for Text or Graphics. JPEG may be good with gradients and details, but it doesn’t handle sharp edges, text, and flat-color illustrations very well. Logos, screenshots, or graphic design elements often appear fuzzy or pixelated.
No Transparency Support. JPEG doesn’t support either single-transparency or full-transparency. It means that if you need to cut out an object and replace the background to a transparent one, you will need to save your image as PNG. Otherwise, the background will be solid white, not transparent.
Not Ideal for Post-Processing. You might’ve heard that professional photographers prefer to shoot in RAW. That’s because RAW formats store much – MUCH – more information in an image file than JPEG. This information is vital if you want to edit your image afterwards. For instance, if you underexposed an image, it will be much easier to brighten it if it’s in RAW. There’s an exception, though. Adobe Photoshop doesn’t support RAW – it requires a certain plugin called Camera Raw. So, if you want to do some skin retouching, you’ll need to work with a JPEG image.
Color Degradation in Low Bit Depth. JPEG typically uses 8-bit color depth per channel (24-bit total), which is usually enough. But in some cases, it can lead to banding, where color transitions appear in stripes rather than smooth gradients.

When Should You Use JPEG?

Use JPEG when:

You’re working with photos, especially if they are full of details, texture, and color gradients.
File size matters. For example, if you need to upload an image to social media or send it via email or a messaging app.
You want fast load times on your website.
You don’t plan on editing your image heavily and in multiple stages.

Avoid JPEG when:

You need transparency (use PNG or WebP instead).
The image contains lots of text or sharp edges.
You need to retain every pixel. For instance, if you’re working with medical or forensic imaging (use a lossless format like TIFF or PNG).
You’re editing the image in multiple stages.

Watermarkly’s Tools for JPEG

Basic editing can help you with sharing and storing your images easily as well as optimizing your visual content for the web.

Here are the online tools available on Watermarkly’s website:

Crop JPEG. Cropping is both easy and powerful. By cropping your image, you can remove distractions and visual noise, and improve composition to make your image well-balanced and focus on what’s important. If there’s sensitive content close to the edge of the frame, you can simply crop it out. This is also how you can change the aspect ratio of your image to meet the requirements of a certain social media platform. For instance, you can crop your photo in JPEG to the 4:5 aspect ratio for a portrait-oriented Instagram post.

Resize JPEG. If you are not entirely sure what resizing is, it means changing the pixel dimensions of an image while maintaining the original aspect ratio. Resizing can help you meet size requirements, too. But what’s more important, you can actually upscale your JPEG image using Watermarkly. Say, you have a 500x500px image that you want to post on Instagram. But for it to look good, it needs to be around 1080 x 1080 px. You can easily achieve that! Just import your image into Watermarkly and enter new pixel dimensions. Don’t worry, your image will get bigger without any pixelation or blurriness!

Compress JPEG. Naturally, JPEG is already a compressed format, but further optimization is often necessary. But by compressing them further, you can decrease their file size quite dramatically. For example, you can compress your 9 MB image to 1 MB without any visible difference! Publishing compressed JPEGs on your website is essential for its faster performance because small-sized files will load quicker on a web page.

Watermark JPEG. Watermarks can be incredibly beneficial to photographers, digital artists, entrepreneurs, and pretty much anyone who often shares their content online. Why? They can prevent unauthorized use and distribution as well as promote your brand and increase brand recognition. Adding a website name or logo can actually drive traffic back to you.

Blur a part of a JPEG image. Our blurring app blurs faces and license plates automatically. But you can add a blurring area manually, too.

Blurring objects in an image can help to:

Hide sensitive information. You can crop out private info if it’s close to the edge of the frame. But what if it’s in the middle of your image? In that case, you can opt for blurring instead! Blurring faces, license plates, ID numbers, or home addresses protects privacy.
Comply with regulations. In many countries, sharing identifiable personal data in photos (this includes people’s faces) may violate privacy laws like GDPR.

Last, but not least, you can use Watermarkly to convert other formats to JPEGs. JPEG isn’t always the best format, but it’s the most compatible, and that’s exactly why converting to JPEG can be useful in many situations.

On Watermarkly’s website, you can convert:

PDF to JPEG – You can view a JPEG on pretty much any device, while PDFs aren’t always mobile-friendly. Also, JPEGs embed more easily into HTML, PowerPoint, or Word.

PNG to JPEG – PNG is lossless and larger; converting to JPEG can decrease the file size quite drastically. This can help with faster loading on mobile and older devices. But keep in mind that PNG supports transparency, while JPEG does not!

WEBP to JPEG - WEBP isn’t supported everywhere, especially on older browsers, email services, or offline apps. Additionally, JPEG is more suitable for print than WEBP, which is geared toward web optimization.

HEIC to JPEG – HEIC is Apple’s default (used in iPhones and iPads), but it isn’t always supported on Windows, Android, or older apps. Plus, most online platforms still prefer JPEG.

Keep in mind that converting from a lossless format to JPEG is a one-way street. The compression is irreversible.

Conclusion

JPEGs are an integral part of everyday digital life. This format’s been around for over three decades and still dominates the Internet thanks to its universal compatibility and excellent size-to-quality ratio. Of course, JPEG does have its limits. It doesn’t support transparency and isn’t great for text-heavy images and graphics. And if you are planning on editing your image repeatedly, JPEG won’t be a good choice, either.

Now that you know what JPEG stands for, how it works, what it’s best for, and what Watermarkly’s tools you can use for some basic editing, you’ll be able to get the most out of your digital images.