Rio uses less memory than Arc on the same 10 sites
With the same 10 sites open on one MacBook Pro, Rio added 3,573 MB of memory and Arc added 5,385 MB. That is 1,812 MB less for Rio, about a third. Rio's figure is the mean of 3 runs on an empty test profile; Arc's is 1 run on a profile in daily use, with its extensions.
The result
One overnight run on November 11, 2026, on a MacBook Pro with an Apple M4 Max and 36 GB on macOS 26.6.2. The same 10 public sites opened in each browser, and the number is how much memory those sites added.
| Browser | Version | Runs | Memory the 10 sites added |
|---|---|---|---|
| Rio | 158.0.8127.18 | 3,393 MB, 3,578 MB, 3,749 MB | 3,573 MB (mean) |
| Arc | 1.172.2 | 5,385 MB | 5,385 MB |
5,385 minus 3,573 is 1,812. With the same tabs open, Rio needed 1,812 MB less, about a third less than Arc. Even Rio's highest run, 3,749 MB, is 1,636 MB below Arc.
The 10 sites
- wikipedia.org
- news.ycombinator.com
- developer.mozilla.org
- bbc.com
- github.com
- nytimes.com
- youtube.com
- reddit.com
- stripe.com
- figma.com
They are a normal day's mix: a reference site, news front pages, video, a code host, a design tool and a payments site.
How it was measured
- Launch the browser and give it 60 seconds to settle. Take the first reading.
- Open the 10 sites.
- Wait until they load, plus 30 seconds. Take the second reading.
- The memory the sites added is the second reading minus the first.
Each reading is the physical footprint of every process that belongs to the browser, summed. That is the figure Activity Monitor shows in its Memory column. Which processes belong to which browser is decided the way macOS decides it, by each process's responsible app.
Rio ran 3 times on an empty test profile. Arc ran once on a profile in daily use, with its extensions and tabs, so the number that compares between the two is the memory the same 10 sites added. Live sites change from run to run, which is why Rio's three runs are 3,393, 3,578 and 3,749 MB rather than one number.
What 1,812 MB means on your Mac
On a Mac with 16 GB of memory, 1,812 MB is about 11% of it. That is room the rest of your apps keep while the same 10 tabs stay open in Rio.
Rio also closes tabs you've stopped using. Today tabs you haven't opened for 12 hours move to the archive by default, and each profile can set 24 hours, 7 days or 30 days. Archived tabs are closed and wait in the Library until you want them again.
Check your own Mac
Activity Monitor shows memory per process. Open it, choose the Memory tab and search for the browser's name. Rio's processes show up under Rio. Add them up before and after opening the same set of tabs, and you have your own version of this test.
Speed too
Memory is one half. On Speedometer 3.1, Rio scored 97.8 with Chrome at 100 on the same Mac, and BrowseRating's published scores put Arc at 91.0% of its Chrome score, on a different Mac. The details are in Rio on Speedometer 3.1.
If you are moving from Arc, Rio brings your spaces, pinned tabs, folders and favorites over in one step.
Questions
Does Rio use less memory than Arc?
On one MacBook Pro with the same 10 sites open, Rio added 3,573 MB (mean of 3 runs) and Arc added 5,385 MB (1 run). Arc ran on a profile with extensions, so only the added memory compares.
Which sites were open?
wikipedia.org, news.ycombinator.com, developer.mozilla.org, bbc.com, github.com, nytimes.com, youtube.com, reddit.com, stripe.com and figma.com.
Why compare the memory the sites added?
Arc ran on a profile in daily use, with its extensions and tabs, and Rio ran on an empty test profile. The memory the same 10 sites added is the number that compares between the two.
What counts as memory here?
The physical footprint of every process that belongs to the browser, summed. It is the figure Activity Monitor shows in its Memory column.
