As far as I know, there is no limit... except for the maximum filesize determined by the operating system and the performance degradation you are willing to put up with.

I've peaked out at well over 100kB before (during a scraper storm) with no ill effects except a slight slow-down serving pages/resources.

Jim

My top level .htaccess is currently ~ 650k with no apparent speed degradation on Apache 1.3.x, RewriteLogLevel 2.

The file's a whopper because it's chock-full of commented-out lines/notes to myself, like this snippet courtesy of a 2005 Jim Morgan post:) --

## BLOCK *Faked* blank referer -OR- UA (malicious agents supply a literal hyphen as UA string)
## either the referrer or the user-agent to be a literal "-", which is a rare but nasty exploit
## [webmasterworld.com...]
RewriteCond [from that post; etc.]

-- so actual commands probably weigh in at ~200k, give or take.

Entries are in sections so the server doesn't have to process the entire file for every single hit. (Higher-level RewriteLogs are eye-poppers!)

For example, I have a BANNED UAs section with loads of [NC,OR] conditions ending in a single [F,L] rule. Other sections include BANNED IPs, BANNED HOSTs; there are even monthly sections where I keep an eye on new, iffy visitors (...if I have time to get really, really obsessive:)

The sectional scheme is also a plus because if I goof up one section's code, I don't lose ALL protections.

FWIW