A YouTube description has two jobs: help YouTube’s algorithm understand your video, and persuade a viewer who’s already clicked to keep watching. Most creators treat it as an afterthought. Here’s how to write one that does both jobs well.

YouTube Description Structure — What to Include

Element	Where	Why it matters
Keyword-rich hook	First 125 chars	Shown in search results before “Show more”
Video summary	After hook	Keyword signals for the algorithm
Timestamps	Middle section	Chapters improve watch time and navigation
Call to action	After summary	Subscribe, comment, related video
Links	Lower section	Website, social media, tools mentioned
Hashtags (2–3)	End	Categorisation signal, shown above title in search

The 125-Character Rule

YouTube and Google display only the first 125 characters of a description before the “Show more” cutoff. This is the most important part of the description — it’s the text viewers see in search results before deciding whether to click.

What to put there: a sentence that contains your primary keyword and communicates the value of the video. Not a channel intro, not a disclaimer, not your social links.

Example (bad): “Welcome to my channel! Don’t forget to like and subscribe. Follow me on Instagram @…”
Example (good): “Free AI YouTube title generator that runs on your computer — no subscription, no data sent to the cloud.”

How to Write a Good YouTube Description — Step by Step

1. Identify your primary keyword — what search query should this video rank for? Use it naturally in the first sentence.
2. Write the hook (first 125 characters) — lead with the value, not pleasantries.
3. Expand in 2–3 sentences — what will viewers learn? What problem does the video solve?
4. Add timestamps — for videos over 5 minutes, list chapters with times (00:00 Intro, 01:30 Step 1…).
5. Write a call to action — give viewers a specific next step, not just “subscribe.”
6. Add links and 2–3 hashtags at the end — relevant hashtags, not generic ones.

YouTube Description Best Practices

• Include your primary keyword in the first sentence — this is the strongest description SEO signal
• Use secondary keywords naturally throughout — don’t stuff; write for humans, let keywords appear organically
• Write at least 150 words — very short descriptions give the algorithm less signal
• Don’t copy-paste the same description across videos — duplicate content is penalised
• Update descriptions on old videos — re-optimising an old description can revive rankings on underperforming videos

Does the YouTube Description Affect SEO?

Yes — significantly. YouTube’s algorithm uses description text to understand the topic of a video. Google also indexes YouTube descriptions and can surface them in web search results. The description is one of the most underused SEO levers available to creators — most viewers don’t read it, but the algorithm does.

Use AI to Write Your Description

DescriptionCraft is a free desktop app that generates a complete, structured YouTube description from your video title. It’s built around the 125-character rule and VidIQ’s description best practices. Runs locally on your computer — Mac, Windows, or Linux. No account, no subscription, your video topics stay private.

Frequently Asked Questions

What should I write in my YouTube description?

Start with a keyword-rich sentence in the first 125 characters. Follow with a 2–3 sentence summary of the video, add timestamps if relevant, include a call to action, list any links mentioned, and end with 2–3 hashtags. That structure covers everything YouTube’s algorithm looks for and everything a viewer needs.

How long should a YouTube description be?

YouTube allows up to 5,000 characters. Most effective descriptions are 150–300 words. Longer descriptions work well for tutorials where detailed step-by-step text adds value; shorter descriptions are fine for simple videos.

Can I edit a YouTube description after posting?

Yes — you can edit it any time in YouTube Studio. Re-optimising descriptions on older underperforming videos is one of the fastest ways to improve their search rankings without creating new content.

Do hashtags in YouTube descriptions help?

Yes, but use 2–3 specific ones. YouTube shows the first 3 hashtags above the video title in search results. Use hashtags that match real search terms your audience uses — specific is better than generic.

Want a free tool to write your descriptions? Download DescriptionCraft — free, offline, no sign-up needed.

Want it done for you? Use DescriptionCraft, then check the result with the description and tag counter.

Adding timestamps? Format them with the chapters generator.