firefox - MAILTO max-length of each internet browsers?

Question

Update: Two years before this question, a similar question was asked: Effective maximum mailto: body lengths as pointed out by Peter O. Luckily answers of both questions are complementary :-) Browsers evolved a lot in the last two years, therefore we can say this question is an update of the other one ;-)

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The specifications does not limit the mailto command length:

1. RFC 6068 specification
2. HTML 4 specification (mailto command is an URL)
   (please see this SO answer, the answers of this SO question and the comment of this one)

Therefore the mailto command length depends on internet browser implementations.

I guess very old browsers could not handle mailto commands using more than 255 characters well.

However, nowadays, memory size is no longer an issue about mailto command length.

What is the mailto max-length of the most common internet browsers?

Should be interesting to see whether browsers converge to the same mailto length limitation.

Answer 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"