Web Artifacts Builder
anthropics/skills
Builds multi-component claude.ai HTML artifacts as a small React, TypeScript and Tailwind project, then bundles it into one shareable HTML file.
A skill your agent uses when applies to all <video elements in HTML.
Install Video Thumbnail
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnail --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/video-thumbnail .claude/skills/video-thumbnail && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .claude/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnailType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnail --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/video-thumbnail .agents/skills/video-thumbnail && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .agents/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnail --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/video-thumbnail .cursor/skills/video-thumbnail && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .cursor/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/thedaviddias/Front-End-Checklist.git --path skills/video-thumbnail--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnail --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/video-thumbnail .gemini/skills/video-thumbnail && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .gemini/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnailInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/video-thumbnail .github/skills/video-thumbnail && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .github/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install thedaviddias/Front-End-Checklist video-thumbnail --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/video-thumbnail .opencode/skills/video-thumbnail && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "video-thumbnail" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/video-thumbnail into .opencode/skills/video-thumbnail/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "video-thumbnail", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
video-thumbnail- GitHub stars
- 74k
- Token cost
- ~939 tokens
- SKILL.md length
- 462 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when applies to all <video elements in HTML.
- Applies to all <video elements in HTML
- SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Video Thumbnail is an agent skill from thedaviddias/Front-End-Checklist. Use when applies to all <video elements in HTML. The poster attribute specifies the URL of an image to show as a placeholder before the video is loaded or played. This is distinct from captions or audio descriptions, which are accessibility requirements. The poster is primarily a UX and performance enhancement, though the lack of a poster can indirectly create a CLS (Cumulative Layout Shift) issue if video dimensions are not declared.
Its SKILL.md is about 940 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).
It sits in Frontend & Design. The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.
When your agent uses it
- Applies to all <video elements in HTML
Example prompts
- “/video-thumbnail”
What it can do on your machine
Read from SKILL.md and the folder at commit e8d14d0. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
frontendchecklist.io
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Video Thumbnail loads about 939 tokens when it runs, and up to ~1.8k if it reads all its reference files. Until then it costs about 115 tokens; SKILL.md has 462 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 462 words, ~939 tokens.
Download SKILL.mdSave it as
.claude/skills/video-thumbnail/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- video-thumbnail
- description
- Use when applies to all `<video>` elements in HTML. The `poster` attribute specifies the URL of an image to show as a placeholder before the video is loaded or played. This is distinct from captions or audio descriptions, which are accessibility requirements. The poster is primarily a UX and performance enhancement, though the lack of a poster can indirectly create a CLS (Cumulative Layout Shift) issue if video dimensions are not declared.
- metadata.category
- html
- metadata.priority
- medium
- metadata.difficulty
- beginner
- metadata.estimatedTime
- 10
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/html/video-thumbnail
Add thumbnail images to videos
Without a poster image, a <video> element displays as a blank black rectangle until the first frame is loaded. This is visually jarring, provides no context about the video content, and can cause layout shift (CLS) if the video dimensions are not specified separately. A good thumbnail image communicates the video topic at a glance, allows users to decide whether to play, and improves the page's visual quality — especially on slow connections where video preloading is delayed.
Quick Reference
- Add a
posterattribute to<video>elements with a URL to a representative thumbnail image - The poster image displays before the video loads and while the user decides whether to play
- Poster images improve perceived performance by showing meaningful content before video data arrives
- The poster should accurately represent the video content — deceptive thumbnails violate user trust
- Use an image ratio matching the video's aspect ratio (typically 16:9) and a resolution of at least 1280×720
Check
Find all <video> elements. For each, check that: (1) a poster attribute is present with a non-empty URL; (2) the URL resolves to a valid image (no 404s); (3) the width and height attributes or CSS dimensions are set to prevent layout shift while the poster loads; (4) the poster image accurately represents the video content (not a clickbait or unrelated image).
Fix
(1) Add a poster attribute to each <video> element: <video poster='thumbnail.jpg' controls>. (2) Use an image that represents the video content — typically a frame from the video, a title card, or a branded thumbnail. (3) Ensure the poster image has the same aspect ratio as the video (usually 16:9). (4) Recommended poster dimensions: 1280×720px minimum for HD video; 640×360px is acceptable for smaller embeds. (5) Host the poster image at a CDN-cached URL to ensure fast loading. (6) Also set width and height on the <video> element to prevent CLS.
Show full SKILL.md (149 more words)Show less
Explain
The HTML poster attribute on <video> specifies a URL for an image to display before video playback begins. When preload='none' or preload='metadata' is set (recommended for performance — avoids downloading video data on page load), no video frame is available for display, making the poster image the only visual content visible to the user before play. Without a poster, users see either a black rectangle or a browser-rendered blank video frame, which provides no context. The poster also plays a role in perceived performance — users on slow connections see meaningful content immediately rather than waiting for even the first video frame to load.
Code Review
Review templates, server-rendered HTML, and shared components that output markup related to Add thumbnail images to videos. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/html/video-thumbnail
© thedaviddias, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/video-thumbnail of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Video Thumbnail next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Video Thumbnail this skillthedaviddias/Front-End-Checklist | 74k | — | ~939 | Automated safety check: Pass | MIT | |
| Web Artifacts Builderanthropics/skills | 180k | 40 repos | ~769 | Automated safety check: Pass | Apache-2.0 | |
| React Doctormakeplane/plane | 61k | 12 repos | ~657 | Automated safety check: Pass | AGPL-3.0 | |
| Impeccablebestofjs/bestofjs | 3.1k | 26 repos | ~2.6k | Automated safety check: Pass | MIT | |
| Figma Design System Builderwarpdotdev/warp | 65k | 2 repos | ~4.4k | Automated safety check: Pass | AGPL-3.0 | |
| Web Interface Guidelines Reviewervercel-labs/openreview | 1.7k | 97 repos | ~308 | Automated safety check: Pass | None |
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Related
Categories
Questions about Video Thumbnail
What does Video Thumbnail do?
A skill your agent uses when applies to all <video elements in HTML. Video Thumbnail is an agent skill from thedaviddias/Front-End-Checklist. Use when applies to all <video elements in HTML.
When should I use Video Thumbnail?
Video Thumbnail fits situations like: applies to all <video elements in HTML.
How do I install Video Thumbnail in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a claude-code`. Or copy the skill folder (skills/video-thumbnail in thedaviddias/Front-End-Checklist) into .claude/skills/video-thumbnail in your project. Claude Code loads it when a task matches its description.
How do I install Video Thumbnail in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a codex`. Or copy the skill folder (skills/video-thumbnail in thedaviddias/Front-End-Checklist) into .agents/skills/video-thumbnail in your project. Codex loads it when a task matches its description.
Can I use Video Thumbnail in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add thedaviddias/Front-End-Checklist --skill video-thumbnail -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/video-thumbnail, .gemini/skills/video-thumbnail, .github/skills/video-thumbnail and .opencode/skills/video-thumbnail in your project.
What does Video Thumbnail need to run?
SKILL.md names no scripts, command-line tools or credentials: Video Thumbnail is instructions for the agent only.
Does Video Thumbnail access the network?
SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.
Is Video Thumbnail safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Video Thumbnail use?
Video Thumbnail is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Video Thumbnail use?
About 939 tokens (SKILL.md is roughly 3.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 837 tokens, read only when the agent opens those files.
What are the alternatives to Video Thumbnail?
Skills that share tags, products or a category with Video Thumbnail: Web Artifacts Builder (anthropics/skills, 180k stars), React Doctor (makeplane/plane, 61k stars), Impeccable (bestofjs/bestofjs, 3.1k stars) and Figma Design System Builder (warpdotdev/warp, 65k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Video Thumbnail?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,421 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.
Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.