Benchmark · 5 October 2026
150 tabs on a quarter of the memory.
On one Windows PC, Vesper kept 150 real websites open in 4,394 MB of memory. The only other browser that reached 150 tabs needed 18,409 MB; the other three stopped at 88 or 46 tabs with 20 to 24 GB in use.
Measured 5 October 2026 on Windows 11 · Vesper development build on CEF 154 · each number is the median of 3 rounds.
The result
| Browser | Tabs open | Memory, MB | Peak memory, MB | Idle CPU, s | Processes |
|---|---|---|---|---|---|
| Vesper (development build) | 150 | 4,394 | 6,868 | 167.5 | 39 |
| Browser A | 150 | 18,409 | 18,653 | 236.8 | 188 |
| Browser B | 88 | 20,405 | 21,454 | 132.5 | 262 |
| Browser C | 88 | 20,254 | 21,456 | 138.8 | 229 |
| Browser D | 46 | 24,012 | 27,950 | 600.0 | 196 |
Download: benchmark.csv (these numbers) · benchmark-sites.txt (the 150 sites, in order).
- Vesper kept all 150 tabs open in every round, holding 4,394 MB: 4.2 times less memory than the only other browser that also kept 150 tabs open (18,409 MB).
- Two other browsers stopped near 88 tabs and one near 46, already holding 20 to 24 GB, because the PC ran low on memory.
- Vesper ran 39 processes for 150 tabs; the other browsers ran between 188 and 262.
What each number means
- Tabs open: how many of the 150 pages the browser had open when the test ended.
- Memory: memory held by all of the browser's processes (private bytes, also called commit), 7 minutes after the last tab was opened.
- Peak memory: the highest memory the browser held at any check during the run.
- Idle CPU: CPU seconds the browser used between 1 and 7 minutes after the last tab, with nothing being done.
- Processes: the browser's processes still running 7 minutes after the last tab.
How it was run
- One browser at a time on the same Windows PC (Intel Core, 31.8 GB of memory), with a new temporary profile and default settings; one browser ran as a guest without sync.
- The same 150 public sites in the same order, one per tab, every 3 seconds, with no sign-in, no search and nothing typed or clicked.
- A browser stopped opening tabs when the PC had less than 5 % of its memory free (or less than 8 % of its commit limit), so no browser could push the PC into failure.
- Three rounds in alternating order; each published number is the median.
- Vesper was a development build on CEF 154. The other four are widely used browsers in their current public versions on the test date, named here as Browser A to D.
The 150 sites
News, video, shopping, reference, developer, travel, sport, social and web-app pages that open without an account, so tabs are about as heavy as a person's real tabs. The full list, in order, is in benchmark-sites.txt.
Limits
- One PC, one date, these 150 sites. Other machines, sites or versions can give other numbers.
- Vesper was a development build, not a release.
- Page load speed was not measured.
- With the browsers idle, Browsers B and C used less CPU time than Vesper, with about 60 fewer tabs open.
Why Vesper uses less memory
A feature called Tide lets tabs you have not looked at in a while rest. They keep their place in the tab list and come back where you left them. When memory is tight, at most 12 pages stay awake, and a page with text you have typed, audio playing or a question waiting for you is never put to rest. Ads and trackers are blocked before they load, so their scripts never use memory at all.
Questions about the method
Write to contact@vesper-ai.us. We answer, and we correct this page when something is wrong.