Being able to consume media without the fluff of sponsors, being reminded to sub, intros and outros built into the video makes this a special extension, especially when you can do it on normal videos and music videos. Not only is this a crowdsourced extension that everyone contributes to, but you can too! If you see a video not have the sponsorblock added, please contribute if it needs it!
It's fantastic at what it does and I cannot recommend it any further than the highest praise. Make sure to check out this developer's work. Very smart, very helpful and very user-friendly!

10 months later:
It seems I cannot mark a full video as "Unpaid/Self Promotion" without it going away upon refresh. This extension was phenomenal before, it can be again.

It works most of the time but the submission rules are unclear and they refuse to edit the wiki to clarify

On Android it doesn't seem to actually skip the sponsors but it highlights them, the extension also causes the full screen video to flip orientation to vertical when interacting with the video. Works great on desktop though

Great when it works, but prone to just breaking and not skipping sponsor segments, with no way to get it working again other than uninstalling and reinstalling.

Works all in all but has some minor problems. Sometimes it freezes on segments and there are numerous bad segments where you won't be able to upload yours.

with uBlockOrigin, some video still have segments skip at wrong time.(example: 0:10 - 0:20 is sponsor, SponsorBlock showed 0:10 - 0:20 is sponsor, but it will auto skip from 0:05 to 0:15)
2024/07/18 edit:
popular addon: Enhancer for YouTube™ > ✅Automatically select a playback quality
are cause this issue. please resolve this issue with each other since both are popular addons for youtube

If you ignore the snobby assholes who make nonsense, harmful segments towards small youtubers, it's not half bad.

Absolutely tanks performance when watching youtube videos. Finally narrowed it down to this plug-in. CPU temps spike to 90c+, thermal throttles and brings the performance down.

To dev: Please let me know if I can provide logs or something to help resolve this. This is a really handy extension but its unusable in its current state.

Device: mid-2014 Macbook Pro 13 inch.

Suddenly, advertisements began apper, which I had long forgotten about, apparently YouTube had created a countermeasure. Fix please)

fantastic when it works. major stability issues, frequent outages, recently it has been highlighting sections but just not skipping them. frustrating.

It skips the ads, however, often it does not show green sections on the timeline, nor the adjusted video length in brackets until I refresh the page, then they both show up.

This started happening around a week ago. Before then it was working perfectly.

Description is quite horrible!
Addon has many categories for skips... Addon isn't limited to just sponsors!
Users can update, correct and vote for skipped fragments.

The interface for editors is quite slow and messy and doesn't show audio track or even volume levels in 5.1.13...

I also saw some odd extra frames out of nowhere in 5.1.13 with times suggested from frame by frame navigation by YouTube. Avoid :999 and use :0 or :9 instead sometimes... Nice numbers :64 are better than :63...

Don't be mad if you come across a sub optimal skip somewhere, because at the moment they are not so easy to edit... Really smooth skips can take a dozen tries for some videos...

good but could be better

The add-on overall is very good and works flawlessly. The issue arises when it comes to the segments that are submitted as sponsors. You will have videos with segments that are NOT sponsor content and still people will upload it as a sponsor segment. A perfect example of this is LTTs' YT channel. Where there are often a lot of videos where the content being displayed is sponsored but the information being given isn't related to the sponsor.

Edit: Please implement some sort of minimum time submission! It's getting ridiculous in some videos where people are submitting "sponsor" segments that are less than 5 seconds long and often are literally not even sponsored material.

Server down right now, many server issues within last week, no update regarding the situation