# Compress photos: a simple tutorial for beginners A phone photo often weighs 3 to 5 MB: too much for an e-mail, a website or an online form. This tutorial explains why, then shows you how to make it lighter in a few clicks, without sending anything over the Internet. - Mini-course : Beginner - URL : https://ressources.online/outils/compresser-photo/tutoriel/en/ - Open the tool : https://ressources.online/outils/compresser-photo/ - Updated on 2026-09-27 ## What you will learn - Tell the difference between a photo's size in pixels and its file size in KB or MB. - Pick the right format (JPEG, WebP or PNG) and the right setting for each use. - Shrink up to 30 photos at once and save them to your computer or phone. - Protect your privacy by removing the GPS location hidden in your photos. ## Understanding photo file size ### Pixels and file size: two different measures A digital photo is a mosaic of tiny coloured dots called **pixels**. A recent phone takes photos of about 4000 × 3000 pixels, which is 12 million dots, and sometimes far more (up to 48 million). The **file size**, often called its “weight”, is how much storage the file takes up. It is measured in **kilobytes (KB)** and **megabytes (MB)**: 1 MB equals 1000 KB. A phone photo usually weighs 3 to 5 MB. The two are linked but not the same thing: more pixels means a heavier file, but the way those pixels are stored matters just as much as how many there are. Yet a typical computer screen only shows about 2 million pixels (1920 × 1080). So to look at a photo on screen, 12 million pixels is far more than you need. ### Why your photos are so heavy Phone makers want photos you can zoom into, crop or print in a large format. So they record as much detail as possible, including subtle shades the eye never notices on a screen. The result: ten holiday photos quickly add up to 40 MB. That is too much for most e-mail services, which refuse attachments over 20 to 25 MB. It is too much for a website as well: a page full of heavy photos takes several seconds to appear on a phone using 4G, and Google notices. And many online forms (official paperwork, job applications, insurance claims) reject any file over 1 or 2 MB. The good news: for on-screen use, you can divide that weight by 10 with no visible difference. ### Resizing and compressing: what the tool does There are two ways to make a photo lighter. - **Resizing**: reducing the number of pixels. Taking the long side from 4000 down to 2000 pixels divides the number of pixels by 4, and the file size roughly follows. - **Compressing**: storing the pixels more cleverly. **Lossy** compression (JPEG, WebP) removes the least visible details, such as very slight variations in a blue sky. **Lossless** compression (PNG) keeps every pixel exactly as it was, but saves much less space. The **quality** setting (from 40 to 95 in the tool) controls how much lossy compression is applied. Between 75 and 85, the difference is invisible on screen. Below 60, small blurry squares or smudges may appear around edges. Be careful: lossy compression cannot be undone. Always keep the original, especially if you want to print the photo. ### JPEG, WebP, PNG: which format should you choose? - **JPEG** (.jpg files): the universal photo format, readable everywhere for over thirty years. The best choice for an e-mail, social networks or an online form. - **WebP**: a newer format created by Google, 25 to 35% lighter than JPEG at the same quality. All recent browsers and WordPress accept it, which makes it ideal for a website. Some older software and some official portals do not accept it yet. - **PNG**: lossless and able to keep transparency. Perfect for a logo or a screenshot, but too heavy for a photo. What about **HEIC**? It has been the iPhone's photo format since 2017. It is very efficient, but Windows and most browsers cannot open it. The good news: when you choose your photos on the iPhone itself, it converts them to JPEG automatically. ### The information hidden in your photos Besides the image itself, every photo carries **metadata**, known as **EXIF**: the date and time it was taken, the phone model, the camera settings and, very often, the exact **GPS coordinates** of the place. That is handy for sorting your memories, much less so once the photo leaves your phone. A photo of your living room in a classified ad, or sent as an e-mail attachment, can reveal your home address to anyone who knows how to read this data. The big social networks usually strip the location when you post, but e-mail, websites and some sharing services keep it. The tool rebuilds each photo from the image alone: the new versions contain none of this information. The “GPS location removed” badge tells you which photos had one. > Key takeaway : On screen, a photo doesn't need 12 million pixels: resizing and then compressing it divides its file size by about 10, with no visible loss. Keep the original for printing. ## Words to know - **Pixel** : The smallest coloured dot in a digital image. A 4000 × 3000 pixel photo contains 12 million of them. - **KB and MB** : Units of file size: 1 megabyte (MB) equals 1000 kilobytes (KB). A phone photo weighs 3 to 5 MB, a photo ready for e-mail about 300 KB. - **Lossy compression** : A method that makes a file lighter by removing the least visible details. Used by JPEG and WebP, it cannot be undone. - **Lossless compression** : A method that makes a file lighter without changing the image at all. Used by PNG, it saves far less space on a photo. - **WebP** : A recent image format, 25 to 35% lighter than JPEG, designed for websites. - **HEIC** : The default photo format on iPhones. Efficient, but poorly supported by Windows and most browsers. - **EXIF** : Information hidden in a photo: date, camera model, settings and often the GPS location. ## Shrinking your photos step by step ### Step 1 : Choose your photos Open the [Compress photos](https://ressources.online/outils/compresser-photo/) tool. Click **Choose photos**, or drag them straight into the box from a folder on your computer. On a phone, the button opens your photo gallery. You can process **up to 30 at once**, in JPEG, PNG, WebP and other formats. The work starts right away, on your device: nothing is sent over the Internet. > Tip : On an iPhone, open the tool on the phone itself: your HEIC photos will be converted automatically. ### Step 2 : Say what the photos are for Under “What are they for?”, click the card that matches your need: - **E-mail**: 1600 pixels, good quality, very light; - **Website**: 1920 pixels, in WebP format; - **Social networks**: 2048 pixels, high quality; - **Online form**: under 1 MB per photo. You can switch to another use at any time: the photos are recalculated automatically. ### Step 3 : Fine-tune with the detailed settings For a special need, open **Detailed settings**. You will find four settings: **Size (long side)**, from 800 px to 3840 px or “Original size”; **Format** (JPEG, WebP or PNG); **Quality**, from 40 to 95; and **Maximum weight**, from “No limit” to 5 MB. As soon as you change a setting, the tool switches to custom mode and recalculates. A short note under the settings reminds you what the chosen format is good for. > Tip : A website asks for “500 KB maximum”? Choose 500 KB under Maximum weight: the tool finds the best quality under that limit. ### Step 4 : Read the result Each photo appears in the list with its dimensions and file size **before → after**, for example “4032 × 3024 · 4.2 MB → 1600 × 1200 · 310 KB”. A badge shows how much you saved (for example “−93%”). The **“GPS location removed”** badge flags a photo that contained the place where it was taken. If a photo was already light, the tool leaves it as it is and says so: “Already light: kept as is”. At the top of the list, the total sums up the starting and final file sizes. ### Step 5 : Compare before and after To check the quality, click the **Compare before / after** button to the right of the photo. A window opens: drag the slider, or the image itself, to see the original on one side and the lighter version on the other. Tick **Actual size (see details)** to look at the pixels up close. If the difference bothers you, raise the quality in the detailed settings. ### Step 6 : Get your photos You have three options: - the **Download** button next to a photo, to save just that one; - **Download all (.zip)**, to get every photo in a single compressed file; - on a phone, **Share**, to send them straight to a messaging or e-mail app. The new photos keep their original name followed by “-small”, for example `birthday-small.jpg`: your originals are never changed. **Remove all** clears the list. > Tip : On Windows, right-click the .zip file and choose “Extract All” to get your photos out. ## Practical cases ### Sending photos of the association's party Martine wants to e-mail 20 photos of the spring party held by “Les Jardins de Clara”, a community garden association. Together they weigh 80 MB, and her e-mail service refuses to send them. She picks the 20 photos, keeps the **E-mail** use, then clicks **Download all (.zip)**. Each photo now weighs about 300 KB: the total drops to 6 MB and fits in a single message. Along the way, the GPS locations, which pointed to a member's garden, have disappeared. ### Faster pages for a holiday cottage website The “Gîte des Trois Épis”, a holiday cottage, shows 25 bedroom photos on its WordPress site. On a phone using 4G, the page takes several seconds to appear. The owner runs his photos through the **Website** use: 1920 pixels in WebP format. He replaces the old images in the WordPress media library. The page becomes much lighter, visitors wait less, and Google, which measures page speed, takes note. He can check the result with the [complete website diagnosis](https://ressources.online/outils/diagnostic/). ### A document rejected by an online form For an insurance claim, Paul's insurer asks for a photo of an invoice, “1 MB maximum”. His photo weighs 3.8 MB and the site rejects it. He chooses the **Online form** use. The tool finds the best possible quality under 1 MB and reduces the size slightly if needed. With **Compare before / after** and **Actual size**, Paul makes sure the amounts are still readable, then uploads his photo. ## Common mistakes - Overwriting or deleting the original: lossy compression cannot be undone, so always keep the original photo. - Printing a photo compressed for the screen: for a paper print, start again from the original at its original size. - Choosing PNG for a photo: the file stays heavy, so keep this format for logos and screenshots. - Setting the quality too low: below 60, flaws appear, so check with Compare before / after. - Posting a photo taken at home without removing its metadata: the GPS location can reveal your address. ## The essentials - The number of pixels and the file size in KB or MB are two different but linked things. - For screens, 1600 to 2048 pixels are enough: resizing and compressing divides the file size by about 10. - JPEG for sharing anywhere, WebP for a website, PNG for logos and screenshots. - Photos made lighter by the tool no longer contain the GPS location or any other hidden information. - Everything happens in your browser: your photos are never sent anywhere. ## Test yourself 1. A 4000 × 3000 pixel photo weighs 4 MB. What should you do before e-mailing it? - [ ] Convert it to PNG so that it is lossless - [x] Resize it to 1600 pixels and compress it as JPEG - [ ] Send it as it is: e-mail accepts anything Resized and compressed as JPEG, it drops to about 300 KB, with no visible difference on screen. PNG would actually make it heavier. 2. Which format suits photos on a website best? - [x] WebP - [ ] PNG - [ ] HEIC WebP is 25 to 35% lighter than JPEG and accepted by every recent browser: pages load faster. 3. What can a photo taken with a phone reveal? - [ ] Only its size in pixels - [ ] The phone's unlock code - [x] The date, the phone model and often the exact place where it was taken This metadata (EXIF) can give away your home address. The versions created by the tool no longer contain it. 4. You want a photo printed in a large format. What do you do? - [ ] Use the version compressed for e-mail - [x] Start again from the original photo - [ ] Choose quality 40 to save space Compression is made for screens. For printing, you need all the pixels and all the quality of the original. --- Source : https://ressources.online/outils/compresser-photo/tutoriel/en/ (Ressources.online, Compress photos)