Shopify
Per Shopify's own file-upload documentation, these are hard platform limits — every store, no exceptions:
- Image file size: maximum 20 MB
- Resolution: maximum 25 megapixels
- Aspect ratio: between 100:1 and 1:100
- Supported formats: JPEG, PNG, WEBP, HEIC, and GIF
Source: Shopify Help Center — Uploading and managing files.
WordPress
WordPress itself doesn't set a fixed upload limit — your hosting provider does, at the server level (via upload_max_filesize and post_max_size). In practice this commonly lands somewhere between 2 MB and a few hundred MB depending on host and plan, and WordPress Multisite specifically defaults to a much lower 1.5 MB unless a site owner raises it. There's no single correct number to quote here — check your own limit under Media → Add New in your WordPress dashboard, which displays it directly.
Email attachments
- Gmail (personal accounts): 25 MB total per email, for all attachments combined. Google Workspace accounts can have a different limit set by an admin.
- Outlook.com: 25 MB per message.
- Microsoft 365 / Exchange (organizational accounts): commonly defaults to 35 MB per message, and an admin can raise it up to 150 MB — this varies by organization, so check with yours if it matters.
Sources: Gmail Help — attachment limits, Microsoft Support — sending limits in Outlook.com.
One practical wrinkle: email attachments get encoded (MIME/base64) before sending, which inflates size by roughly a third. A file just under a stated limit can still get rejected — a safer target is about 25% below the number above.
What this means for your images
If you're bumping into one of these limits, compressing your images first is usually the fix — smaller file size, same picture. Image Compressor handles one image at a time for free; Batch Image Compressor (QuickTiny Pro, $4.99 one-time) does a whole folder in one pass.
One important distinction: compression reduces file size, not pixel dimensions. If a platform's limit is about width/height (like Shopify's aspect-ratio rule, or a theme's image-dimension requirement) rather than file size, compression alone won't fix it — you'd need a separate resizing step.
Frequently asked questions
Does compressing an image change its dimensions?
No. QuickTiny's compressors reduce file size at the same width and height — they don't crop, scale, or resize.
Will a 20 MB Shopify-sized image actually fit Gmail's 25 MB limit?
It might not, once encoding overhead is factored in. Compressing it down first is the safer move if you're emailing product photos rather than uploading them directly.
How do I check my actual WordPress upload limit?
Go to Media → Add New in your WordPress dashboard. The maximum upload size for your specific hosting setup is shown right above the upload area.
Do these numbers ever change?
Yes — platforms adjust limits over time. These were verified against each provider's own documentation in September 2026; check the source links above if you need the current figure for something time-sensitive.