How to Compress Images for Email on Mac

You took a great photo on your iPhone. You want to email it. The problem: your mail client rejects it, the recipient's inbox bounces it, or it just takes forever to send because it's 8MB. This is a daily frustration for anyone using a modern smartphone camera.

The fix is simple — but most people don't know the fastest way to do it on a Mac without sacrificing quality or uploading their photos to a stranger's server.

Why email images are so large

Modern smartphone cameras — especially iPhones with 48MP sensors — produce massive files. A single RAW or even a compressed HEIC from the Camera Roll can be 6–15MB. Email providers typically allow 10–25MB total per message, which means you can often attach only one or two photos before hitting the limit.

The issue is made worse by format. iPhones save photos as HEIC by default, which many email clients and recipients on Windows or older systems can't open. So you often need to both convert and compress before attaching.

What size should images be for email?

As a rule of thumb:

• For inline photos in email body: 500KB–1MB per image is ideal. Readers don't need 48MP resolution to view an image in an email.
• For attachments the recipient will download and use: 1–3MB per image strikes the right balance between quality and deliverability.
• For sending originals to a client or printer: Use a file sharing service (Dropbox, WeTransfer) instead of email. Email is not the right tool for full-resolution delivery.

Method 1: macOS Preview (built-in, limited)

macOS Preview has a basic export function that lets you resize and re-export images:

1. Open your image in Preview.
2. Go to File → Export.
3. Choose JPEG, reduce the quality slider to 60–75%, and save.

This works for one image at a time. It has no batch mode, no HEIC conversion, and the quality slider is imprecise. For occasional use it's fine. For anything more than one or two photos, it's too slow.

Method 2: A dedicated local app (recommended)

TinyPixels handles compression and batch processing entirely locally on your Mac. No upload, no accounts, no per-image fees.

1. Drop your photos (JPG, PNG, WebP — any supported format) into TinyPixels.
2. Set the output format to JPEG and quality to 75–85%.
3. Hit Convert. Files are saved to your chosen output folder.
4. Attach the compressed versions to your email.

A batch of 20 iPhone photos that would have been 160MB total becomes 15–25MB — all in under 10 seconds on Apple Silicon.

Why not just use an online tool?

The obvious alternative is dragging your photos to TinyPNG, Squoosh, or a similar browser-based tool. These work, with caveats:

• You're uploading personal photos to a third-party server.
• Most have file size limits (TinyPNG caps at 5MB per image).
• Batch processing is painful or unavailable.
• You need an internet connection.

For personal photos — especially those with family members, locations, or anything you'd consider private — the local approach is simply better practice. The convenience difference between a dedicated app and an online tool is minimal. The privacy difference is significant.

Quick reference: target file sizes by use case