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Developer tools
Developer tools
100 questions
How to open the developer console?
•
F12 or Ctrl+Shift+I (Cmd+Option+I on Mac).
•
Right-click → Inspect.
•
Console tab for logs and commands.
•
Ctrl+Shift+J — directly to console (Chrome).
•
Page errors are displayed here.
How to emulate a mobile device?
•
Open DevTools (F12).
•
Press Ctrl+Shift+M or click the device icon.
•
Select a device from the list.
•
Or set size manually.
•
Emulates touch events and User-Agent.
How to find CSS styles of an element?
•
Open DevTools.
•
Ctrl+Shift+C — element selection mode.
•
Click on the element on the page.
•
The Styles tab shows applied styles.
•
Computed — computed values.
How to clear cache for a single site?
•
DevTools → Application tab (Chrome) or Storage (Firefox).
•
Clear storage / Clear site data.
•
Or right-click on the refresh button → 'Clear cache and hard reload'.
•
Works with DevTools open.
How to simulate a slow connection?
•
DevTools → Network tab.
•
Dropdown 'No throttling'.
•
Choose: Slow 3G, Fast 3G, Offline.
•
Or create your own profile.
•
Test loading under poor internet conditions.
Developer tools: how to read requests/responses in Network and find errors?
Start with simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: how to profile performance (Performance/Lighthouse)?
Practice for 'Developer tools': test in incognito mode and in another browser. It's quick to identify whether the problem is in the site or in profiles/extensions.
Developer tools: how to debug JavaScript and set breakpoints?
Answer for 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
For 'Developer tools': it's useful to set up a password manager and tracker blocker, but avoid installing dozens of extensions at once.
Developer tools: question №10
If the question is about 'Developer tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: how to read requests/responses in Network and find errors?
Keep your 'Developer tools' profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: how to profile performance (Performance/Lighthouse)?
Start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to debug JavaScript and set breakpoints?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is either in the site or in the profile/extensions.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: question №15
For 'Developer Tools', it is useful to set up a password manager and tracker blocking, but do not install dozens of extensions at once.
Developer Tools: how to read requests/responses in Network and find errors?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: how to profile performance (Performance/Lighthouse)?
For 'Developer Tools', keep the profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to debug JavaScript and set breakpoints?
On the topic of 'Developer Tools', start simple: update the browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is either in the site or in the profile/extensions.
Developer Tools: question №20
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to read requests/responses in Network and find errors?
For 'Developer Tools', it is useful to set up a password manager and tracker blocking, but do not install dozens of extensions at once.
Developer Tools: how to profile performance (Performance/Lighthouse)?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: how to debug JavaScript and set breakpoints?
Keep your 'Developer Tools' profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Start with simple steps on 'Developer Tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: question №25
Practice for 'Developer Tools': check in private mode and in another browser. This quickly shows whether the problem is with the site or your profile/extensions.
Developer tools: how to read requests/responses in Network and look for errors?
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to profile performance (Performance/Lighthouse)?
For 'Developer Tools', it is useful to set up a password manager and tracker blocker, but avoid installing dozens of extensions at once.
Developer tools: how to debug JavaScript and set breakpoints?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site issues.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Keep your 'Developer Tools' profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: question №30
Start with simple steps on 'Developer Tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: how to read requests/responses in Network and look for errors?
Practice for 'Developer Tools': check in private mode and in another browser. This quickly shows whether the problem is with the site or your profile/extensions.
Developer tools: how to profile performance (Performance/Lighthouse)?
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to debug JavaScript and set breakpoints?
For 'Developer Tools', it is useful to set up a password manager and tracker blocking, but not to install dozens of extensions at once.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: question №35
Regarding 'Developer Tools', keep your profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to read requests/responses in Network and find errors?
On the topic of 'Developer Tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to profile performance (Performance/Lighthouse)?
Practical for 'Developer Tools': check in private mode and in another browser. This quickly shows whether the problem is in the site or in your profile/extensions.
Developer Tools: how to debug JavaScript and set breakpoints?
Answer about 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
For 'Developer Tools', it is useful to set up a password manager and tracker blocking, but not to install dozens of extensions at once.
Developer Tools: question №40
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: how to read requests/responses in Network and find errors?
Regarding 'Developer Tools', keep your profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to profile performance (Performance/Lighthouse)?
On the topic of 'Developer Tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to debug JavaScript and set breakpoints?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is either on the site or in your profile/extensions.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: question №45
For 'Developer Tools' it is useful to: set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer Tools: how to read requests/responses in Network and find errors?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: how to profile performance (Performance/Lighthouse)?
For 'Developer Tools' keep your profile clean: periodically remove unused extensions and reset settings when problems accumulate.
Developer Tools: how to debug JavaScript and set breakpoints?
On the topic of 'Developer Tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is either on the site or in your profile/extensions.
Developer Tools: question №50
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to read requests/responses in Network and find errors?
For 'Developer Tools' it is useful to: set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer Tools: how to profile performance (Performance/Lighthouse)?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: how to debug JavaScript and set breakpoints?
Keep your 'Developer tools' profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Start with simple steps on 'Developer tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: question №55
Practice for 'Developer tools': check in incognito mode and in another browser. This quickly shows whether the problem is with the site or your profile/extensions.
Developer tools: how to read requests/responses in Network and look for errors?
Answer for 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to profile performance (Performance/Lighthouse)?
For 'Developer tools', it is useful to set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer tools: how to debug JavaScript and set breakpoints?
If the question is about 'Developer tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Keep your 'Developer tools' profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: question №60
Start with simple steps on 'Developer tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: how to read requests/responses in Network and look for errors?
Practice for 'Developer tools': check in incognito mode and in another browser. This quickly shows whether the problem is with the site or your profile/extensions.
Developer tools: how to profile performance (Performance/Lighthouse)?
Answer for 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to debug JavaScript and set breakpoints?
For 'Developer Tools', it is useful to set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: question №65
Regarding 'Developer Tools', keep your profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to read requests/responses in Network and find errors?
On the topic of 'Developer Tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to profile performance (Performance/Lighthouse)?
Practice for 'Developer Tools': check in incognito mode and in another browser. This quickly shows whether the problem is with the site or with your profile/extensions.
Developer Tools: how to debug JavaScript and set breakpoints?
Answer about 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
For 'Developer Tools', it is useful to set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer Tools: question №70
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: how to read requests/responses in Network and find errors?
Regarding 'Developer Tools', keep your profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to profile performance (Performance/Lighthouse)?
On the topic of 'Developer Tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to debug JavaScript and set breakpoints?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is in the site or in the profile/extensions.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: question №75
For 'Developer Tools' it is useful to: set up a password manager and tracker blocking, but do not install dozens of extensions at once.
Developer Tools: how to read requests/responses in Network and find errors?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer Tools: how to profile performance (Performance/Lighthouse)?
For 'Developer Tools' keep the profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer Tools: how to debug JavaScript and set breakpoints?
On the topic of 'Developer Tools', start simple: update the browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer Tools: how to work with Application/Storage (cookies, localStorage)?
Practice for 'Developer Tools': check in private mode and in another browser. It's quick to understand — the problem is in the site or in the profile/extensions.
Developer Tools: question №80
Answer for 'Developer Tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer Tools: how to read requests/responses in Network and find errors?
For 'Developer Tools' it is useful to: set up a password manager and tracker blocking, but do not install dozens of extensions at once.
Developer Tools: how to profile performance (Performance/Lighthouse)?
If the question is about 'Developer Tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: how to debug JavaScript and set breakpoints?
Keep your profile clean in 'Developer tools': periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Start with simple steps in 'Developer tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: question №85
Practice for 'Developer tools': check in incognito mode and in another browser. This quickly reveals whether the problem is with the site or your profile/extensions.
Developer tools: how to read requests/responses in Network and look for errors?
Answer for 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to profile performance (Performance/Lighthouse)?
For 'Developer tools': it is useful to set up a password manager and tracker blocker, but do not install dozens of extensions at once.
Developer tools: how to debug JavaScript and set breakpoints?
If the question is about 'Developer tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site issues.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
Keep your profile clean in 'Developer tools': periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: question №90
Start with simple steps in 'Developer tools': update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: how to read requests/responses in Network and look for errors?
Practice for 'Developer tools': check in incognito mode and in another browser. This quickly reveals whether the problem is with the site or your profile/extensions.
Developer tools: how to profile performance (Performance/Lighthouse)?
Answer for 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to debug JavaScript and set breakpoints?
For 'Developer tools', it is useful to set up a password manager and tracker blocking, but not to install dozens of extensions at once.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
If the question is about 'Developer tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.
Developer tools: question №95
Regarding 'Developer tools', keep your profile clean: periodically remove unused extensions and reset settings when issues accumulate.
Developer tools: how to read requests/responses in Network and find errors?
On the topic of 'Developer tools', start simple: update your browser, clear cache/cookies for the problematic site, and disable extensions one by one.
Developer tools: how to profile performance (Performance/Lighthouse)?
Practice for 'Developer tools': test in incognito mode and in another browser. This quickly shows whether the problem is in the site or in the profile/extensions.
Developer tools: how to debug JavaScript and set breakpoints?
Answer about 'Developer tools': enable synchronization, but keep 2FA and backup codes. Security is more important than convenience.
Developer tools: how to work with Application/Storage (cookies, localStorage)?
For 'Developer tools', it is useful to set up a password manager and tracker blocking, but not to install dozens of extensions at once.
Developer tools: question №100
If the question is about 'Developer tools', check DNS/proxy/VPN and certificates. Many errors are network-related, not site-related.