MAILTO max-length of each internet browsers?

Solution 1:

Safari and most email clients have no hard limit (depends on available CPU and RAM)

2015 Web Browser Testing:

• Safari
  • 705000000
  • 2 minutes
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/601.1.56 (KHTML, like Gecko) Version/9.0 Safari/601.1.56
  • limited by 16GB RAM
• Firefox
  • 268435455
  • 20 seconds
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:41.0) Gecko/20100101 Firefox/41.0
  • limited by maximum string length
• Chrome
  • 2097132
  • 1 second
  • Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36
  • limited without explanation
• IE
  • 2029
  • 5 seconds
  • Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; rv:11.0) like Gecko
  • limited without explanation

2015 Email Client Testing:

• Mozilla Thunderbird
  • 2097132 works in 1 second
  • 268435455 uses 100% CPU for 2 minutes but fails to render the body and is not usable
  • version 38.3.0
• SeaMonkey
  • 2097132 works in 5 seconds
  • 268435455 uses 100% CPU for a long time (more than 5 minutes)
  • version 2.38
• Apple Mail
  • 500000 works in 14 seconds
  • 2097132 uses 100% CPU for a long time (more than 5 minutes)
  • version 8.2
• Microsoft Outlook
  • trims to 2070 in 1 second
  • version 2013

2017 update

Chrome 61 still works with 2097132 length on macOS (16 GB RAM);

navigator.userAgent;
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36"
location.href='mailto:?body='+'a'.repeat(2097132);

According to @Chloe on windows (32 GB RAM) it's limited to 1800;

"Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36"

Solution 2:

Just for reference I've found that google chrome's latest build (23.0.1271.95) only lets me generate a mailto with a maximum length of:

1910 characters