What it is. Data transferred out to visitors — HTML, JSON, images, fonts, scripts, video. Measured in GB per billing period.
What makes it go up.
- More visitors, or heavier pages.
- Large uncompressed images and video.
- Cache misses — every uncached response is billed again.
- Bots, crawlers and attack traffic. This is the one that surprises people. Neither platform discounts traffic you did not want. A DDoS bills at the standard rate, which is how documented cases reach five figures.
What it costs. Both platforms include an allowance and bill overage per GB. Vercel meters it per project; Netlify counts it against your account allowance or credits.
How to reduce it.
- Cache aggressively. Long
s-maxageplusstale-while-revalidateon anything not per-user. Single biggest lever. - Compress and right-size images. Serve modern formats. Do not ship a 2000px image into a 400px slot.
- Put a CDN or WAF in front if bot traffic is a recurring problem — especially on Netlify, which has no spend cap.
- Rate-limit the expensive routes.
Related: Why is my Vercel bill so high?
Watch it before it bites
MONII tracks Vercel and Netlify usage and alerts at a threshold you choose, with a kill switch to pause a runaway project.
Get MONII for iOS ›