Cloud data transfer costs: egress on Azure, AWS, Google
Egress is data sent out of a cloud to the internet. It is the charge that surprises people most, because you do not buy it like a server. It appears as a line on the bill that grows with every response you send to a user.
The basic rule
Data coming in from the internet is free on all four clouds. Data going out is billed per gigabyte. Price per gigabyte generally falls as monthly volume rises, in steps called tiers, so the first gigabytes cost the most.
| Cloud | The line on the bill |
|---|---|
| Azure | Bandwidth (Microsoft network routing) |
| AWS | Data transfer out |
| Google Cloud | Network egress (Premium Tier) |
| Oracle Cloud | Outbound data transfer |
Some clouds also offer a cheaper but slower route, such as Google’s Standard Tier. We compare each vendor’s default, premium-quality route, because that is what most people get without changing anything.
Where clouds differ
The free allowance. Each cloud gives a monthly amount of free outbound data, and the amounts differ and change over time. For a small site, the free allowance can cover the whole bill. For a larger one it hardly matters.
The tiers. The step points and the price in each step differ. Two clouds that look close at 100 GB a month can be far apart at 10 TB. This is why the estimator lets you change the data out figure and see how the totals move.
The destination. Google prices data out by where it goes, so a site with users in India is billed differently from one with users in the US. The estimator assumes users are near the region you pick.
Traffic that is not internet egress
Not every byte that leaves a server is internet egress, and the other kinds are billed separately:
- Between zones in one region, such as an app server talking to a database in another zone.
- Between regions, such as copying backups to a second region.
- To other services through public addresses instead of private links.
These charges are easy to miss because they do not look like user traffic. Our estimates cover only data out to internet users.
Ways to reduce it
- Use a CDN for images, scripts and downloads, so repeat requests are served from a cache. Our estimates do not include a CDN, so adding one lowers the bill below what we show.
- Compress responses. Text formats such as HTML, JSON and CSS shrink a lot.
- Keep chatty services in the same zone, where the provider and design allow it.
- Check large downloads, such as exports and backups. One heavy user or a bot can send a large share of your total.
Estimate yours
Use the web app estimator and change the data out figure. The data transfer compare page shows each cloud’s price lines and tiers with a link to the vendor’s page. For the whole bill, see what a web app costs.