youtube goes full screen automatically

I looked back, and am embarrassed to admit that I skipped it.

I just tried it - toggled full screen and then returned to the small screen.

This ameliorated the issue: now when I click on a youtube video, it plays and remains in the small screen.

Thank you, tybg.

And thanks Eric for bringing tygb's suggestion to my attention again.

I found ~/Library/Safari/LocalStorage, which seemed to contain Safari cookies. I copied this folder to the desktop, then deleted it from its original location. Then I launched Safari, navigated to Preferences > Privacy > Manage Website data. All the cookies appeared. I then cleared all using the Safari Preferences interface. The cookies disappeared. I quit Safari and relaunched it. The cookies reappeared, and Youtube videos behaved the same, moving to full-screen without being commanded to do so. Cookies are clearly being stored somewhere in addition to ~/Library/Safari/LocalStorage. If I use Firefox, youtube videos stay in a small window.

This is perplexing: I have a second Mac I used for travel, a mid-2013 MacBook Air. The Air's OS and software is an exact mirror of my main machine's setup...but youtube videos on the Air don't behave this way - when clicked on to view, they stay in small window mode. There's obviously something different in the two setups.

Thanks for your responses. I guess I'll just launch FF when I want to youtube.

Hi dominic, that makes sense, but I can't see how to do it in practice. Apple has placed two cookies, and my ISP and bank one each. But I have almost a thousand others, and while I can easily locate the four ones to keep, macOS won't let me mark them for retention. Thus, I think I'd have to go through the whole list line by line to delete the others. That's too much work.

I'm tempted to delete all of them, to see what happens. Cookies would be replaced by their issuers (my Safari settings obviously allow it), and Keychain and I know my passwords.

Thanks for spending time with me on this!

1. Did that. "Begin using Safari" didn't appear. Youtube behaved the same as before.

2. Here's the Etrecheck report:

EtreCheck version: 3.4.6 (460)

Report generated 2017-10-14 13:12:29

Download EtreCheck from https://etrecheck.com

Runtime: 3:07

Performance: Good

Click the [Lookup] links for more information from Apple Support Communities.

Click the [Details] links for more information about that line.

Problem: Other problem

Description:

youtube videos go to full screen automatically

Hardware Information: ⓘ

MacBook Pro (13-inch, Mid 2010)

[Technical Specifications] - [User Guide] - [Warranty & Service]

MacBook Pro - model: MacBookPro7,1

1 2.4 GHz Intel Core 2 Duo (Duo) CPU: 2-core

4 GB RAM Upgradeable - [Instructions]

BANK 0/DIMM0

2 GB DDR3 1067 MHz ok

BANK 1/DIMM0

2 GB DDR3 1067 MHz ok

Handoff/Airdrop2: not supported

Wireless: en1: 802.11 a/b/g/n

Battery: Health = Normal - Cycle count = 273

iCloud Quota: 5.00 GB available

Video Information: ⓘ

NVIDIA GeForce 320M - VRAM: 256 MB

LA1951 1280 x 1024 @ 60 Hz

Disk Information: ⓘ

Crucial_CT250MX200SSD1 disk0: (250.06 GB) (Solid State - TRIM: No)

[Show SMART report]

EFI (disk0s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB

MBP SSD (disk0s2 - Journaled HFS+) / [Startup]: 249.20 GB (125.45 GB free)

Recovery HD (disk0s3 - HFS+) <not mounted> [Recovery]: 650 MB

MATSHITADVD-R UJ-898 ()

USB Information: ⓘ

USBBus

Apple Inc. BRCM2046 Hub

Apple Inc. Bluetooth USB Host Controller

Apple Computer, Inc. IR Receiver

Apple Inc. Apple Internal Keyboard / Trackpad

USBBus

USB20Bus

Apple Inc. Built-in iSight

USB 2.0 Hub [MTT]

HP Deluxe Webcam KQ246AA HP Deluxe Webcam KQ246AA

Burr-Brown from TI USB Audio DAC

Mitsumi Electric Hub in Apple Extended USB Keyboard

Microsoft Basic Optical Mouse

Mitsumi Electric Apple Extended USB Keyboard

USB 2.0 Hub

Western Digital My Passport 259F

My Passport 259F disk1: (1 TB)

EFI (disk1s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB

TM 3 (disk1s2 - Journaled HFS+) /Volumes/TM 3 : 999.83 GB (802.47 GB free)

USB20Bus

Apple Card Reader

System Software: ⓘ

macOS Sierra 10.12.6 (16G29) - Time since boot: about 2 hours

Gatekeeper: ⓘ

Mac App Store and identified developers

Kernel Extensions: ⓘ

/Library/Extensions

[loaded] com.usboverdrive.driver.hid (3.3 - SDK 10.9) [Lookup]

/Library/Extensions/USBOverdrive.kext/Contents/PlugIns

[not loaded] com.usboverdrive.driver.bt (3.3 - SDK 10.9) [Lookup]

[not loaded] com.usboverdrive.driver.hid.safe (3.3) [Lookup]

/System/Library/Extensions

[not loaded] com.iospirit.driver.rbiokithelper (1.7.2) [Lookup]

Startup Items: ⓘ

Macaroni: Path: /Library/StartupItems/Macaroni

RetroRun: Path: /Library/StartupItems/RetroRun

Startup items no longer function in OS X Yosemite or later

System Launch Agents: ⓘ

[not loaded] 8 Apple tasks

[loaded] 180 Apple tasks

[running] 97 Apple tasks

System Launch Daemons: ⓘ

[not loaded] 40 Apple tasks

[loaded] 179 Apple tasks

[running] 99 Apple tasks

Launch Agents: ⓘ

[failed] com.adobe.ARMDCHelper.cc24aef4a1b90ed56a725c38014c95072f92651fb65e1bf9c8e43c37a2 3d420d.plist (Adobe Systems, Inc. - installed 2017-01-10) [Lookup]

[running] com.epson.Epson_Low_Ink_Reminder.launcher.plist (EPSON - installed 2017-01-25) [Lookup]

[loaded] com.epson.esua.launcher.plist (Seiko Epson Corporation - installed 2017-07-25) [Lookup]

[running] com.epson.eventmanager.agent.plist (Seiko Epson Corporation - installed 2017-01-25) [Lookup]

[loaded] com.google.keystone.agent.plist (Google, Inc. - installed 2017-09-27) [Lookup]

[not loaded] com.oracle.java.Java-Updater.plist (? 0 ? - installed (null)) [Lookup]

Launch Daemons: ⓘ

[loaded] com.adobe.ARMDC.Communicator.plist (Adobe Systems, Inc. - installed 2017-01-10) [Lookup]

[loaded] com.adobe.ARMDC.SMJobBlessHelper.plist (Adobe Systems, Inc. - installed 2017-01-10) [Lookup]

[loaded] com.apple.installer.osmessagetracing.plist (Apple, Inc. - installed 2017-07-14)

[loaded] com.google.keystone.daemon.plist (Google, Inc. - installed 2017-10-12) [Lookup]

[loaded] com.malwarebytes.HelperTool.plist (Malwarebytes Corporation - installed 2017-02-15) [Lookup]

[loaded] com.microsoft.autoupdate.helper.plist (Microsoft Corporation - installed 2017-02-13) [Lookup]

[not loaded] com.oracle.java.Helper-Tool.plist (? 0 ? - installed (null)) [Lookup]

User Launch Agents: ⓘ

[running] com.c-command.SpamSieve.LaunchAgent.plist (C-Command Software, LLC - installed 2017-08-24) [Lookup]

User Login Items: ⓘ

Faviconographer Application

(/Applications/Faviconographer.app)

Jettison Application

(/Applications/Jettison.app)

MoofMenu Application

(/Applications/Utilities/MoofMenu.app)

USBOverdriveHelper Application

(/Library/PreferencePanes/USB Overdrive.prefPane/Contents/Resources/USBOverdriveHelper.app)

Internet Plug-ins: ⓘ

Flip4Mac WMV Plugin: 2.4.4.2 (installed 2014-03-29) [Lookup]

QuickTime Plugin: 7.7.3 (installed 2017-07-14)

AdobePDFViewerNPAPI: 17.012.20098 (installed 2017-08-30) [Lookup]

AdobePDFViewer: 17.012.20098 (installed 2017-08-30) [Lookup]

o1dbrowserplugin: 5.41.3.0 (installed 2016-04-02) [Lookup]

googletalkbrowserplugin: 5.41.3.0 (installed 2015-12-11) [Lookup]

PDF Browser Plugin: 2.4.4 (installed 2014-07-10) [Lookup]

iPhotoPhotocast: 7.0 (installed 2013-07-08)

User internet Plug-ins: ⓘ

CitrixOnlineWebDeploymentPlugin: 1.0.105 (installed 2013-04-25) [Lookup]

Safari Extensions: ⓘ

[enabled] Adblock Plus - Eyeo GmbH - https://adblockplus.org/ (installed 2017-10-09)

[enabled] Omnikey - Mario Estrada - http://marioestrada.github.com/safari-omnikey/ (installed 2017-09-12)

3rd Party Preference Panes: ⓘ

USB Overdrive (installed 2017-10-13) [Lookup]

Time Machine: ⓘ

Skip System Files: NO

Mobile backups: OFF

Auto backup: YES

Volumes being backed up:

MBP SSD: Disk size: 249.20 GB Disk used: 123.75 GB

Destinations:

TM 3 [Local]

Total size: 999.83 GB

Total number of backups: 64

Oldest backup: 7/19/17, 9:02 AM

Last backup: 10/14/17, 12:42 PM

Size of backup disk: Excellent

Backup size 999.83 GB > (Disk size 249.20 GB X 3)

Top Processes by CPU: ⓘ

6% com.apple.WebKit.WebContent

5% kernel_task

4% Safari

3% hidd

2% WindowServer

Top Processes by Memory: ⓘ

544 MB kernel_task

371 MB Safari

274 MB com.apple.WebKit.WebContent

238 MB com.apple.WebKit.WebContent

162 MB Mail

Top Processes by Network Use: ⓘ

Input Output Process name

1 MB 820 KB Mail

104 KB 35 KB com.apple.WebKit.Networking

34 KB 10 KB mDNSResponder

12 KB 26 KB apsd

12 KB 3 KB netbiosd

Top Processes by Energy Use: ⓘ

7.22 WindowServer

6.00 Finder

4.28 com.apple.WebKit.WebContent

2.64 Safari

Virtual Memory Information: ⓘ

930 MB Available RAM

76 MB Free RAM

3.09 GB Used RAM

854 MB Cached files

0 B Swap Used

Software installs (last 30 days): ⓘ

1Password: (installed 2017-10-02)

1Password: (installed 2017-10-02)

USB Overdrive: (installed 2017-10-09)

USB Overdrive: (installed 2017-10-13)

Install information may not be complete.

Diagnostics Events (last 3 days for minor events): ⓘ

2017-10-14 10:33:52 Last shutdown cause: 3 - Hard shutdown

2017-10-13 14:04:18 backupd High CPU use [Open] [Details]

2017-10-13 12:03:56 SafariBookmarksSyncAgent Crash [Open]

Cause: dyld: launch, loading dependent libraries

2017-10-13 12:03:54 SafariDAVClient Crash [Open]

Cause: dyld: launch, loading dependent libraries

2017-10-13 11:57:13 Safari.app Crash [Open]

Cause: dyld: launch, loading dependent libraries

2017-10-13 09:55:38 com.apple.WebKit.WebContent Crash [Open]

Cause: Bundle controller class:

BrowserBundleController

Files deleted by EtreCheck: ⓘ

2017-10-12 17:57:24 - ~/Library/LaunchAgents/com.example.mytest.plist - Unknown

2017-10-12 17:57:41 - com.adobe.ARM.[...].plist - Unknown

2017-10-12 17:57:41 - com.apple.CSConfigDotMacCert-@me.com-SharedServices.Agent.plist - Unknown

2017-10-12 17:57:41 - ~/Library/LaunchAgents/com.vladalexa.MagicPrefs.plist - Unknown

My system meets the requirements.

But look at my answer to Eric Root, above: your earlier suggestion (to manually toggle full screen and then untoggle it) solved the problem. I had passed over your post without trying. Employing it this morning, youtube acted as it should.

I appreciate your help, thank you!

Removing the youtube cookie was the first thing I tried.

I just tried it again. Doing so did not change this behavior.

The debug menu isn't enabled, and I didn't change any setting there.