I used to send photos and screenshots from iPhone to my PC or Mac via email and edit them with Photoshop. If you have attached multiple high quality images to email, the stock Mail app will automatically reduce file size of photos in email. It can scale images to different sizes with quality loss. If you are not happy with the quality loss, you can give a shot to the free iZip app which you reduce image size with a little quality loss or zip photos without compression or quality loss.
Go to download the zip & unzip app here first. Note that the free version is not ads-free and you will be prompted to upgrade to the premium version from time to time. You can batch zip up to 10 photos each time with the free version. If you like the app, you may consider upgrading to unlock all features and remove the annoying ads. Also we will use the stock Files app on iPhone to compress files without any third-party apps at the lower section of this article. In fact, you can try the Files app before you download extra zip apps.
1. Compress iPhone photos using iZip
Run iZip on your iPhone. Allow it the access to your Photo library on the device.
Tap Photos category from its home screen, select the photos, screenshots, images, selfies you like to compress, tap the Zip button at the bottom, you will then have the option to reduce image file size.
Confirm the compression, the selected photos will be compressed as a zip file saved to the Files category. You can then select the zip file, tap Share, select to email the zip file to yourself, upload it to a cloud storage, share with others, send to your PC or Mac from there.
The zip app can help us archive almost all kinds of files, like DOC, Excel, PPT, PDF, TXT, RTF, Pages, JPG, GIF, PNG, audios, videos, just to name a few. Unlike audios, photos & videos archiving, if you like to zip other file types, you need to import them from the Files app to the iZip app first, then create a zip file with them in the iZip app. You can find more details from this tutorial to zip files on iPhone using iZip app.
Zip photos without compression
When you are prompted whether to reduce file size of photos or not, tap on No so the iZip app will zip your photos on iPhone iPad without compression or quality loss.
2. Compress photos using Files app on iPhone
The stock Files app for iOS can also help us compress or archive files, folders on our iPhone iPad. Open the Photos app to find and choose the images or photos you want to compress, then choose Share > Save to Files. Fire up the Files app to find the pictures, tap the Select button at the top right corner, then choose the More button (three dots) at the bottom right corner to bring up the options at the lower section on your phone screen.
Choose Compress. A zip archive will be created and saved to the same folder as the original files or folders in Files app on your iPhone.
Update May 2020: this article was originally published in Apr 2019 and has since been updated. In this update, we added the solution to compress files and documents using the stock Files app on iPhone without downloading extra apps.