Now I have comprehensive information to compile a thorough answer. Let me present this to the user.

🖼️ Keyless & Simple URL-Based Website Screenshot Services

Here is a comprehensive list of website screenshot services that provide simple URL query templates — many requiring no API key or signup (keyless), and others with generous free tiers.

🟢 1. WordPress mShots API (Completely Keyless)

No API key. No signup. Totally free.

URL Template:

Copyhttps://s0.wp.com/mshots/v1/{url}?w={width}&h={height}

Parameters:

Examples:

Copyhttps://s0.wp.com/mshots/v1/codepen.io?w=1200&h=700
https://s0.wp.com/mshots/v1/codepen.io?w=800&h=500
https://s0.wp.com/mshots/v1/codepen.io

Source: CodePen Demo

🟢 2. Eleventy (11ty) Screenshot API (Completely Keyless)

No API key. Open source. Free forever.

URL Templates:

Copyhttps://v1.screenshot.11ty.dev/:url/
https://v1.screenshot.11ty.dev/:url/:size/
https://v1.screenshot.11ty.dev/:url/:size/:aspectratio/
https://v1.screenshot.11ty.dev/:url/:size/:aspectratio/:zoom/

Parameters:

Example:

Copyhttps://v1.screenshot.11ty.dev/https%3A%2F%2Fwww.11ty.dev%2Fdocs%2F/small/9:16/bigger/

Source: 11ty Docs

🟢 3. LinkDR Screenshot API (Completely Keyless)

No API key. No signup. No credit card. 100% free.

URL Template:

Copyhttps://linkdr.com/api/screenshot/{domain}

Features:

• Returns 302 redirect to screenshot URL (hot-linkable)
• 1350×900px WebP, 95% quality
• Ad & tracker blocking built-in
• 7-day CDN cache

Example:

Copyhttps://linkdr.com/api/screenshot/github.com

Source: LinkDR Blog

🟢 4. PagePeeker (Keyless / Free)

No signup required for basic usage.

URL Template:

Copyhttp://free.pagepeeker.com/v2/thumbs.php?size={size}&url={url}

Parameters:

Example:

Copyhttp://free.pagepeeker.com/v2/thumbs.php?size=x&url=codepen.io

Source: CodePen Demo

🟢 5. Microlink API (Keyless for 50/day)

No login required. 50 free screenshots/day.

URL Template:

Copyhttps://api.microlink.io/?url={target_url}&screenshot=true

Additional Parameters:

Example:

Copyhttps://api.microlink.io/?url=https://github.com&screenshot=true&meta=false&embed=screenshot.url

Source: Microlink | Mixed Analytics

🟡 6. Thum.io (Free Tier, Auth for Premium)

Free tier with 1,000/month. Hot-linking supported.

URL Template:

Copyhttps://image.thum.io/get/{options}/{url}

Parameters (path-based modifiers):

Examples:

Copyhttps://image.thum.io/get/https://www.google.com/
https://image.thum.io/get/width/300/https://www.google.com/
https://image.thum.io/get/width/500/crop/800/https://www.google.com/
https://image.thum.io/get/?url=http%3A%2F%2Fwww.google.com%2F

Special Modes:

Copy# PDF to Image
https://image.thum.io/get/pdfSource/width/300/{pdf_url}

# Image Resizing
https://image.thum.io/get/image/width/300/{image_url}
https://image.thum.io/get/image/fit/300x200/{image_url}

# Batch Prefetch
https://image.thum.io/get/prefetch/{url}

Source: Thum.io Docs

🟡 7. Cloudflare Workers Screenshot API (Free 500/mo)

Free tier: 500 requests/month. No credit card.

URL Template:

Copyhttps://screenshot-api.t-mizuno27.workers.dev/capture?url={url}&width={w}&height={h}&format={fmt}

Parameters:

Example:

Copycurl "https://screenshot-api.t-mizuno27.workers.dev/capture?url=https://github.com&width=1280&height=720&format=png" -o screenshot.png

Source: Dev.to

🟡 8. Screenshot Machine (API Key Required, Free Tier)

Free tier available. Requires signup.

URL Template:

Copyhttps://api.screenshotmachine.com/?key={KEY}&url={URL}&dimension={DIM}&device={DEV}&format={FMT}

Parameters (16 total):

Source: Screenshot Machine

🟡 9. OpenGraph.io Screenshot API (API Key, Free 5/mo)

5 free screenshots/month. No credit card.

URL Template:

Copyhttps://opengraph.io/api/1.1/screenshot/{encoded_url}?app_id={APP_ID}&dimensions={dim}&quality={q}&full_page={bool}

Parameters:

Source: OpenGraph.io

🟡 10. ScreenshotOne (API Key, 100 Free/mo)

URL Template:

Copyhttps://api.screenshotone.com/take?access_key={KEY}&url={URL}&viewport_width={W}&viewport_height={H}&format={FMT}&full_page={BOOL}

Source: ScreenshotOne

🟡 11. ScreenshotAPI.net (API Key, 100 Free/mo)

URL Template:

Copyhttps://shot.screenshotapi.net/screenshot?token={TOKEN}&url={URL}&width={W}&height={H}&full_page={BOOL}

Source: ScreenshotOne Blog

📊 Quick Comparison Table

💡 Recommendation: For truly keyless usage, WP mShots, 11ty Screenshot API, and LinkDR are the best options — just construct the URL and embed it directly as an <img> tag. For more advanced features (full-page, device emulation, custom delays), Thum.io and the Cloudflare Workers API offer excellent free tiers with minimal friction.