How do I compress an image on a Mac?

Open the image in Preview → File → Export → choose JPEG format → drag the Quality slider to 70–80% → Save. This reduces file size by 60–80% with no visible quality loss at normal viewing sizes. For more control, use a browser-based compressor at compressimg.pro.

How do I reduce image file size in Mac Preview?

Open your image in Preview. Go to File → Export. In the dialog, select JPEG from the Format dropdown. Drag the Quality slider left — 70–80% gives 60–80% file size reduction. Click Save. The exported file is the compressed version; the original is unchanged.

What is sips on Mac and how do I use it to compress images?

sips (Scriptable Image Processing System) is a macOS command-line tool for image processing. To compress: open Terminal and run: sips -s formatOptions 80 --setProperty format jpeg input.jpg --out output.jpg. Replace "80" with your target quality (1–100). You can process multiple files in a loop.

Can I batch compress images on a Mac?

Yes. In Mac Preview, open multiple images → select all (Cmd+A) → File → Export Selected Images → choose JPEG → set quality. Alternatively, use Automator: create a workflow with "Scale Images" and "Change Type of Images" actions. For command-line batch processing, use a sips loop in Terminal.

How do I convert HEIC to JPEG on Mac?

Open the HEIC file in Preview → File → Export → choose JPEG from the Format dropdown → set quality → Save. Or use the sips command: sips -s format jpeg input.heic --out output.jpg. HEIC files from iPhone convert to JPEG without quality loss at this step.

Does macOS have a built-in image compressor?

Not a dedicated one, but Preview handles JPEG compression via File → Export → Quality slider. The sips command-line tool in Terminal is more powerful and supports batch processing. For the most control over quality and output size, use a browser-based tool which lets you see before/after sizes instantly.

Guide·June 23, 2026·7 min read

How to Reduce Image File Size on Mac — 5 Free Methods (2026)

macOS has several built-in tools for reducing image file size — Preview, sips, and ColorSync — plus browser-based options that work without any software at all. This guide covers all five methods with step-by-step instructions, so you can choose the one that fits your workflow.

5 Methods — Quick Comparison

Method	Best for	Quality control	Batch
1. Browser tool	Any image, any Mac	⭐⭐⭐⭐⭐	Up to 5
2. Preview app	Quick one-off	⭐⭐⭐	❌
3. Preview Export	Format convert	⭐⭐⭐⭐	❌
4. sips (Terminal)	Power users	⭐⭐⭐	✅ Unlimited
5. Automator	Recurring tasks	⭐⭐⭐	✅ Unlimited

Method 1 — Browser Tool (No Software, Works on Any Mac)

The fastest method that works on any macOS version, including M1/M2/M3 Macs, without installing anything. All processing happens in your browser — images never leave your device.

Open Safari or Chrome and go to compressimg.pro/compress-image
Drag your image onto the upload area, or click to browse
Adjust the quality slider — 80 is the recommended default (visually lossless for web and email use)
Click Download — the compressed file saves to your Downloads folder

Supports JPEG, PNG, WebP, and HEIC. For multiple images, use the batch compress tool to process up to 5 files at once.

Method 2 — Resize in Preview (Built into macOS)

Preview is macOS's built-in image viewer and editor. It can reduce image file size by resizing the dimensions, which is the most effective way to shrink large photos from iPhone or DSLR cameras.

Open your image in Preview (double-click the file)
Go to Tools → Adjust Size (⌘ + Opt + I)
Change the Width to your target — for web use, 1920px is sufficient for a full-width image; 800px for smaller uses
Make sure Scale proportionally is checked — the height adjusts automatically
Click OK
Save: File → Save (⌘ S) to overwrite, or File → Export to save a new copy

Preview resize results (typical DSLR photo)

Original (4000×3000 px)12 MB

Resized to 1920×1440 px3.2 MB

Resized to 1280×960 px1.4 MB

Resized to 800×600 px400 KB

Method 3 — Export as JPEG in Preview

If your image is a PNG (lossless, large file), exporting it as JPEG with a quality setting dramatically reduces file size. This is the Preview method for controlling compression quality directly.

Open the image in Preview
Go to File → Export
Change Format to JPEG
Drag the Quality slider to around 75–80% — this is the compression sweet spot for most images
Click Save

A 10 MB PNG exported as JPEG at quality 75% typically becomes 500 KB–1.5 MB — a reduction of 85–95% — with no visible difference on screen.

Note on HEIC files

Preview can open HEIC files from iPhone but the Export quality slider behavior differs from JPEG. For HEIC compression with precise quality control, use compressimg.pro/heic-to-jpg instead.

Method 4 — sips Command (Terminal, Power Users)

sips (Scriptable Image Processing System) is a command-line tool built into macOS that can resize, convert, and compress images without any additional software. It is ideal for batch processing large numbers of images.

# Resize a single image to max 1920px wide, keeping aspect ratio

sips -Z 1920 ~/Desktop/photo.jpg

# Convert PNG to JPEG with quality 80

sips -s format jpeg -s formatOptions 80 ~/Desktop/image.png --out ~/Desktop/image.jpg

# Batch resize all JPEGs in a folder to max 1920px

for f in ~/Desktop/photos/*.jpg; do sips -Z 1920 "$f"; done

The -Z flag sets the maximum dimension (longest edge). The -s formatOptions flag sets JPEG quality from 0 (lowest) to 100 (highest). sips modifies images in-place by default — use --out path to save to a new location.

Method 5 — Automator Quick Action (Batch, No Terminal)

Automator lets you create a right-click Quick Action for images, so you can compress any image directly from Finder without opening an app or writing commands.

Open Automator (search in Spotlight)
Choose New Document → Quick Action
Set Workflow receives to image files in Finder
Search for and add the Scale Images action
Set the width to your target (e.g., 1920 pixels)
Optionally add a Copy Finder Items action before Scale Images to preserve the originals
Save with a name like “Compress to 1920px”

After saving, right-click any image or selection of images in Finder → Quick Actions → Compress to 1920px. The images are resized instantly without opening any app.

Target Sizes by Use Case

Use case	Target size	Max dimensions	Best method
Email attachment	< 1 MB	1280×960 px	Method 1 or 3
Website / blog	< 300 KB	1920×1080 px	Method 1
WhatsApp / Messages	< 500 KB	1280×960 px	Method 1 or 3
Form upload (100KB limit)	< 100 KB	600×600 px	Method 1
PowerPoint / Keynote	< 500 KB	1920×1080 px	Method 1
Batch (100+ images)	Varies	Max 1920 px	Method 4 (sips)

Related Tools

Compress image — full quality control, works in Safari on Mac
Batch compress — compress multiple images at once
HEIC to JPG — convert iPhone HEIC photos to JPEG on Mac
Resize image — reduce dimensions to shrink file size
PNG to JPG — convert large PNGs to smaller JPEG files

Frequently Asked Questions

How do I reduce image file size on Mac without losing quality?

Compress to quality 80 using compressimg.pro or Preview's JPEG export. At quality 80, JPEG compression is perceptually lossless — the difference is invisible on screen at normal viewing distance. For PNG files with flat colors (logos, diagrams), keep them as PNG since quality 80 JPEG will introduce artifacts on sharp edges.

Can Preview reduce image file size on Mac?

Yes, in two ways: (1) resize dimensions via Tools → Adjust Size, which reduces file size proportionally to pixel count; (2) export as JPEG via File → Export with the quality slider set to 75–80%. Resizing is the more effective method for large camera photos.

How do I compress images in bulk on Mac?

Use the sips command in Terminal for the most control: `for f in folder/*.jpg; do sips -Z 1920 "$f"; done` resizes all JPEGs in a folder to max 1920px. Alternatively, create an Automator Quick Action with the Scale Images step for a right-click workflow from Finder.

Does Mac have a built-in image compressor?

Yes — Preview can resize and export images at lower quality (effective compression). The sips command-line tool provides more control and supports batch processing. For the best quality-to-size ratio with a visual preview, use compressimg.pro in Safari.

How do I reduce HEIC file size on Mac?

Open the HEIC file in Preview and export via File → Export → Format: JPEG at quality 75–80. Alternatively, use compressimg.pro/heic-to-jpg for more precise control and a before/after size comparison.

Why does my image get larger after saving in Preview?

Preview saves PNG files as lossless by default, which can actually increase file size if the original was a compressed JPEG. Always use File → Export and explicitly choose JPEG with quality 75–80 rather than saving in place, which re-encodes the file in its original format.