Via [url=https://list.valvesoftware.com/]HLDS[/url] and [url=https://store.steampowered.com/news/47741/]the Steam store[/url]:

[quote=Valve]- Improved memory usage on OS X and Linux systems
- This should reduce the occurrence of "Out of memory or address space" errors on high texture quality settings
- In particular, drastically improved memory usage for Linux users using mesa prior to mesa 19.0
- Added Respawn League AUS/NZ Highlander Season 2, AUS/NZ 4v4 Season 1, Asia Highlander Season 1, and Asia 4v4 Season 1 tournament medals
- Added Eu Mixes Cup 1 tournament medals
- Added KnightComp Season 1 tournament medals
- Updated cp_snakewater_final1 to fix missing player clips
- Updated the localization files[/quote]

Rumor has it:

- Size is close to 25 MB

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[b][url=https://support.steampowered.com/kb_article.php?ref=1558-AFCM-4577]Valve's support of Steam on Windows XP and Windows Vista has ended on 1/1/19.[/url] Additionally, [url=https://support.steampowered.com/kb_article.php?ref=5953-QTIO-1764]Valve's support of Steam on Mac OS X Lion, Mountain Lion, Mavericks, and Yosemite also ended on 1/1/19 as well.[/url][/b] Any future TF2 updates that moves the minimum Steam client version beyond the last one available for XP/Vista will render it unplayable unless you upgrade Windows. Any future TF2 updates that moves the minimum Steam client version beyond the last one available for Lion through Yosemite will also render it unplayable unless you grab Mac OS X El Capitan or newer from the Mac App Store.