How to Compress Images on Mac: 6 Methods That Work

A 12 MB photo from your iPhone is great for printing. It is terrible for your website, your email, and your Slack channel. macOS has built-in tools that compress images without installing anything — and when those fall short, a couple of free options fill the gaps.

Here are six methods to compress images on Mac, ranked from quickest to most powerful. Pick the one that fits your workflow.

1. Preview — The Fastest Option You Already Have

Preview ships with every Mac and handles one-off JPEG compression in about five clicks.

Steps (macOS Sequoia 15):

1. Open your image in Preview.
2. Go to File → Export.
3. In the Format dropdown, select JPEG.
4. Drag the Quality slider to set compression level. The slider runs from 0% (smallest file, worst quality) to 100% (largest file, best quality). A setting of 60-70% typically cuts file size by 60-80% with minimal visible loss.
5. Click Save.

Preview shows an estimated file size below the quality slider, so you can dial in exactly the size you need before saving.

Limitations: Preview handles one image at a time. It only offers lossy JPEG compression — there is no lossless option, and no PNG optimization. If you need to compress 50 product photos, keep reading.

For a deeper look at JPEG quality settings and what each level actually removes, see our JPEG compression guide.

2. Photos App — Quick Resize for Sharing

The Photos app is not a compression tool per se, but its export presets reduce file size effectively by resizing and re-encoding.

Steps (macOS Sequoia 15):

1. Open Photos and select one or more images.
2. Go to File → Export → Export [N] Photos.
3. Choose a Photo Kind (JPEG is the default).
4. Under Size, pick Small, Medium, Large, or Full Size.
5. Click Export and choose a destination.

The Small preset (roughly 320px on the long edge) is useful for thumbnails. Medium and Large work for social media and blog posts. Photos also strips location data and other metadata during export, which shaves off a few extra kilobytes and is better for privacy.

Limitations: You get preset sizes, not a quality slider. No fine-grained control over compression ratio. For precise output, use Preview or the sips CLI.

3. sips CLI — Compress Images from the Terminal

sips (Scriptable Image Processing System) ships with macOS and runs from Terminal. It is the fastest way to compress or resize images in a script or one-liner — no GUI, no app switching.

Compress JPEG quality:

sips -s formatOptions 60 photo.jpg

This sets JPEG quality to 60 (out of 100) and overwrites the original. Back up your files first, or write to a new path:

sips -s formatOptions 60 photo.jpg --out compressed/photo.jpg

Resize to a max dimension (preserving aspect ratio):

sips -Z 1920 photo.jpg

This scales the image so the longest edge is 1920 pixels. Smaller images are left untouched. Combine both for maximum savings:

sips -Z 1920 -s formatOptions 65 photo.jpg --out compressed/photo.jpg

Batch compress every JPEG in a folder:

mkdir -p compressed
for f in *.jpg; do
  sips -s formatOptions 60 "$f" --out "compressed/$f"
done

Key flags:

If you regularly resize images on Mac, sips is worth committing to muscle memory.

4. Automator Quick Action — Batch Compression on Right-Click

For repeatable batch compression without opening Terminal, build an Automator Quick Action. Once set up, you right-click any selection of images in Finder and compress them in one step.

Steps (macOS Sequoia 15):

1. Open Automator (search Spotlight for "Automator").
2. Choose Quick Action as the document type.
3. At the top, set "Workflow receives current" to image files in Finder.
4. From the left panel, drag Copy Finder Items into the workflow. Set the destination to a folder like ~/Desktop/Compressed. This preserves your originals.
5. Drag Scale Images into the workflow. Set the size — 1920 pixels works for most web use. Check "By Percentage" if you prefer (e.g., 50%).
6. Optionally, drag Change Type of Images and set it to JPEG if you want to convert PNGs to JPEG during the process.
7. File → Save. Name it something like "Compress Images."

Now select images in Finder, right-click, go to Quick Actions → Compress Images, and the workflow runs automatically.

Shortcuts alternative: On macOS Sequoia 15, the Shortcuts app can do the same thing with the "Convert Image" and "Resize Image" actions. Shortcuts is more modern, but Automator Quick Actions integrate better with Finder's right-click menu.

Limitations: Automator resizes but does not offer a JPEG quality slider. For quality control, use sips in a shell script triggered by Automator's "Run Shell Script" action.

5. ImageOptim — Free, Lossless + Lossy, Drag-and-Drop

ImageOptim (v1.9.1, GPL-2.0 license, free) is the best dedicated compression app for Mac. It runs multiple optimization algorithms in parallel — MozJPEG, pngquant, Zopfli, SVGO — and picks the smallest result.

What makes it good:

• Lossless by default. It strips metadata and re-encodes without quality loss. Typical savings: 20-40%.
• Lossy mode available. Enable "lossy minification" in preferences for 60-80% savings with near-invisible quality loss.
• Drag-and-drop. Drop a folder of images onto the window and walk away.
• Overwrites originals. Files compress in place — no duplicates cluttering your disk. (Back up first if you want to keep originals.)
• Handles JPEG, PNG, GIF, and SVG.

Steps:

1. Download from imageoptim.com/mac and drag to Applications.
2. Open ImageOptim.
3. Drag images or folders onto the window.
4. Wait for the green checkmarks. Done.

For PNG-specific optimization tips, see our PNG compression guide.

Limitations: No resize option — ImageOptim only compresses, it does not change dimensions. Pair it with sips or Preview for resize-then-compress workflows.

6. Pixotter — No Install, Works in Your Browser

If you do not want to install anything, Pixotter's compression tool runs entirely in your browser. Drop your image, pick a target size or quality level, and download the result. Your images never leave your Mac — all processing happens client-side via WebAssembly.

Why use it over the built-in tools:

• Multiple operations in one step. Compress, resize, convert format, and crop — all before downloading. No need to chain Preview, sips, and Photos together.
• Format conversion included. Convert PNG to WebP, JPEG to AVIF, or any combination while compressing.
• Works on any Mac (and any OS). No version dependencies, no Terminal, no Automator setup.
• Visual quality comparison. See before/after side-by-side before committing to a compression level.

For situations where you need to compress and crop an image on Mac in the same step, the pipeline approach saves time over switching between apps.

Method Comparison

How Much Space Will You Save?

Actual savings depend on the image content, starting format, and target quality. Here are realistic expectations for a typical 4032x3024 iPhone photo (about 5-8 MB as HEIC, 10-14 MB as uncompressed JPEG):

For web use, target under 200 KB per image. For email attachments, under 1 MB per image. The sips + resize approach or Pixotter's pipeline gets you there fastest.

Understanding Lossy vs. Lossless

Every method above uses either lossy or lossless compression (or both). The short version: lossy discards data you probably will not notice, achieving much smaller files. Lossless rearranges data more efficiently without discarding anything — smaller savings, but pixel-perfect.

For a full breakdown of when to use each approach, read our lossy vs. lossless compression guide.

Rule of thumb: Use lossy compression (JPEG quality 60-80%) for photos. Use lossless compression for screenshots, diagrams, and anything with text or sharp edges.

FAQ

Does compressing an image reduce its quality?

Lossy compression (like JPEG quality reduction) removes data and can reduce quality if you compress too aggressively. At quality levels of 60-80%, most people cannot tell the difference. Lossless compression (like ImageOptim's default mode) reduces file size without any quality loss.

What is the best image format for small file sizes on Mac?

For photos, JPEG at 70-80% quality offers the best size-to-quality ratio. For graphics with transparency, PNG with lossless optimization. For maximum compression with modern browser support, WebP and AVIF beat both — Pixotter can convert to either format during compression.

Can I compress images in bulk on Mac without installing anything?

Yes. Use the sips CLI in Terminal with a bash loop (see the sips section above), or build an Automator Quick Action for a right-click workflow. Both ship with macOS.

Will compressing images remove my photo metadata (EXIF)?

Preview and sips preserve most metadata. ImageOptim strips metadata by default (configurable in preferences). Photos strips location data on export. If you need to keep metadata, check your tool's settings before compressing.

How do I compress a PNG on Mac?

Preview cannot compress PNGs effectively — it only adjusts JPEG quality. Use ImageOptim (v1.9.1) for lossless PNG optimization, or convert to WebP for much smaller files. Our PNG compression guide covers this in detail.

What JPEG quality level should I use?

For web images: 60-75%. For print or archival: 85-95%. Below 50%, compression artifacts become obvious on most photos. Use Preview's quality slider or sips -s formatOptions 70 to experiment — the estimated file size updates in real time in Preview.

Is Pixotter safe to use for sensitive images?

Yes. Pixotter processes images entirely in your browser using WebAssembly. Your files never leave your Mac — nothing is uploaded to a server. This makes it safe for confidential documents, medical images, or any file you would rather not send to a cloud service.

How do I automate image compression on Mac?

Three options: (1) A sips bash script triggered by a cron job or folder action. (2) An Automator Quick Action attached to Finder's right-click menu. (3) A Shortcuts automation triggered on a schedule or folder change. The sips approach gives the most control; Automator is the most beginner-friendly.