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.
Developer tools: question №95 — Developer tools