Sider AI is a popular browser sidebar that brings multiple AI models (ChatGPT, Claude, Gemini and others) to any page, including YouTube. It has grown rapidly and its YouTube summarization feature is a frequently cited use case. YouTube Spoiler is narrower — built purely for the YouTube thumbnail-hover workflow. Here is how they compare.
What Sider AI Is
Sider is a browser extension that opens a persistent sidebar with access to multiple AI models. You can chat with AI about any page you are viewing, highlight text and explain it, translate content, or generate summaries. On YouTube specifically, Sider can read the video transcript and return a summary within the sidebar.
The breadth of Sider's feature set is its main selling point. If you want an AI assistant that follows you around the entire web — not just YouTube — Sider is a reasonable choice. It competes more with tools like HARPA AI or browser-integrated Copilot features than with YouTube-specific summarizers.
What YouTube Spoiler Is
YouTube Spoiler does exactly one thing: it surfaces an AI summary of a YouTube video when you hover over its thumbnail, before you open the video. It works on the homepage, search results, recommended videos, and channel pages. It streams bullet points in real time, supports 35 languages, and requires no account.
If you are browsing YouTube and want to know whether a video is worth opening, YouTube Spoiler answers that question faster than any sidebar can — because you never have to open the video at all.
Feature Comparison
| Feature | YouTube Spoiler | Sider AI |
|---|---|---|
| Summarize from thumbnail | Yes | No |
| Works on YouTube feed / homepage | Yes | No |
| YouTube summary on watch page | No | Yes |
| AI chat on any web page | No | Yes |
| Multiple AI models (GPT, Claude, etc.) | No | Yes |
| Real-time streaming output | Yes | Depends on model |
| 35-language summary output | Yes | Depends on prompt |
| Account required | No | Yes |
| Free tier | 3 summaries/day, no account | Limited daily queries |
| Pro / unlimited price | $3.99/mo | from ~$8–$12/mo |
Pricing
YouTube Spoiler: 3 free summaries per day (no account), Pro unlimited at $3.99/mo.
Sider AI: a free tier with a daily query limit; paid plans for more queries or access to premium AI models. Pricing has shifted over time — check Sider's website for current rates. An account is required even on the free tier.
When to Use YouTube Spoiler
- You want to triage your YouTube feed before opening any video
- Speed matters — you want summaries in 2 seconds, not after navigating to a watch page
- You do not want to pay for general AI features you will not use
- You want no account friction and immediate use after install
- You need summaries in one of 35 languages without configuring prompts
When to Use Sider AI
- You want an AI assistant across the entire web, not just YouTube
- You need access to multiple AI models (GPT-4, Claude, Gemini) in one place
- You want to chat about the content of a video in depth, not just get a summary
- You use AI for page summarization, text explanation, and translation on non-YouTube sites
The Honest Take
Sider is a solid all-around AI browser assistant. If you need AI help across the web — not just YouTube — it is worth evaluating. The YouTube summary feature is real and functional, though it requires opening the video.
For the specific problem of deciding which YouTube videos to watch, YouTube Spoiler is faster, simpler, and cheaper. The thumbnail-first workflow is genuinely unique. If your frustration is "I open videos that turn out to be a waste of time," YouTube Spoiler addresses that directly. Sider addresses it only partially, and only after you have already clicked.
Frequently Asked Questions
Does Sider AI summarize YouTube videos?
Yes. Sider AI includes a YouTube summary feature that activates on the video watch page. It shows a summary panel alongside the player. However, Sider does not work from thumbnails — you must navigate to the video first. YouTube Spoiler is the only extension that summarizes directly from thumbnails without opening the video.
Is Sider AI free?
Sider AI has a free tier with a daily message/query limit for its AI features. Unlimited access and access to more powerful AI models requires a paid plan (from around $8–$12/mo, though their pricing has changed over time). YouTube Spoiler is free for 3 summaries per day with no account required; Pro unlimited is $3.99/mo.
What makes YouTube Spoiler different from Sider AI?
The biggest difference is where the summary appears. Sider works on the watch page after you have already opened a video. YouTube Spoiler works on thumbnails — on the homepage, search results, and feed — so you can read a summary before deciding to open the video at all. YouTube Spoiler is also focused only on YouTube; Sider covers many websites and use cases.
Can I use both Sider and YouTube Spoiler together?
Yes, they serve different moments. YouTube Spoiler helps you decide which videos to watch from the feed. Sider can then help you get more from the videos you do watch on the watch page. They do not conflict and can be used together.
Related: YouTube Spoiler vs HARPA AI • YouTube Spoiler vs Eightify • Best YouTube Summarizer Extensions