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COMPARING THE APPLICATIONS - SeaMonkey, Mozilla Firefox, and Mozilla Thunderbird

Some people find this to be something of great interest: making and supporting the claim that Firefox and Thunderbird together are faster, use less memory, and take up less disk space. Generally, I don't care. I prefer SeaMonkey and, as I think you'll see, on modern systems the differences in disk footprint, memory, and load times are trivial.

I gathered the results in the following table using the NVST methodology: Not Very Scientific Testing. For the record, here's what I did:


I believe I ran this first set of tests in 2006.

memory virtual memory time to load (from fresh boot) time to load (after start:close sequence) disk footprint
Firefox 1.5 - open to local file 35.8 Mb 27.8 Mb 9 seconds 6 seconds 216 File(s) 20,318,400 bytes
Thunderbird - 1.0.7 to password prompt 22.1 Mb 12.8 Mb 4 seconds 3 seconds 126 File(s) 19,469,045 bytes
Total for FF and TB 57.9 Mb 40.6 Mb 13 seconds 9 seconds 39,787,445 bytes
SeaMonkey Suite 1.0 Beta
- browser - load first 63.2 Mb 52.8 Mb 12 seconds 6 seconds
- mail/news - to password prompt - memory is total of browser and mail/news 64.5 Mb first start - 49.5 Mb second start 54.1 Mb first start - 39.5 Mb second start 3 seconds (after browser loaded) 2 seconds (after browser loaded) 232 File(s) 23,258,601 bytes


The system I got in late 2005:

Yes, on slower and older systems the times would be longer. But I first did this comparison about two years ago on a 933 MHz machine with 512 Mb of RAM. The numbers were a bit different but the differences between FF+TB vs. a Suite application were still trivial. Make up your own mind.

Another interesting thing is the claim that adding a command-line switch (/Prefetch:1) to Firefox will speed up its load time. Near as I can tell this is a complete myth. Not only have I tried it myself on more than one occasion but the following links will, I believe, successfully debunk this myth. It apparently stems from misunderstanding of how the "prefetch" feature of Windows works. This is, by the way, what accounts for the differences in load times in my test and why I did it the way I did. See these links:

For more thoughts on the Suite/SeaMonkey vs. FF/TB please see The SeaMonkey Page.

Okay, somebody asked so I re-ran a simplified version of these tests in November 2013.

The system:

I only did the test after loading and unloading the apps once. Interesting info.

The FF and SM browser profiles are indentical. The TB profile was imported from SM.

memory time to load disk footprint
Firefox 25 - open to local file 205 Mb 11 seconds 193 File(s) 52,613,528 bytes
Thunderbird - 24.1.0 to stable after accounts all loaded 76 Mb 3 seconds 695 File(s) 669,354,633 bytes
Total for FF and TB 281 Mb 14 seconds 721,96,816 bytes
SeaMonkey Suite 2.22
- browser - load first 62 Mb 3 seconds
Total with browser and mail/news - to stable after accounts all loaded - memory is total of browser and mail/news 159 Mb Mail/News - 8 seconds - Total = 11 seconds 232 File(s) 23,258,601 bytes

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