image-specs

Open JSON data for working with images on the web: platform image sizes with official sources, upload size limits, image format properties, and measured conversion and compression results.

Every record either quotes an official source (page URL, word-for-word quote, date checked) or comes from a test run with Pixohub's in-browser tools. Each record links to the Pixohub page that performs the change (resize, compress, convert).

File	Contents	Records
`data/platform-image-sizes.json`	Official dimensions, aspect ratios, upload limits, cropping and safe zones for social, video, marketplace and print placements	93 placements (53 with an official dimension record)
`data/upload-size-limits.json`	File-size and dimension limits for email attachments, exam and visa forms, avatars and marketplaces	83
`data/image-formats.json`	JPG, PNG, WebP, AVIF, HEIC, SVG, GIF, BMP, TIFF, ICO, PSD, TGA, PPM: compression, colour depth, transparency, animation, metadata, support	13
`data/conversion-tests.json`	Format-to-format conversion measured on a photo and a transparent graphic: size change, SSIM/PSNR, alpha and EXIF survival	108 pairs
`data/compression-tests.json`	Compress-to-size (10 KB – 5 MB) on 20 phone photos and the Kodak suite: hit rate, median size, resolution kept, SSIM	23 targets
`data/pixohub-resize-presets.json`	The sizes Pixohub's resize presets produce (working values, not official specs)	143

The same files are served with open CORS at https://pixohub.com/open-data/<file>.json and documented at pixohub.com/developers.

Record shapes

platform-image-sizes.json

{
  "id": "youtube-thumbnail",
  "platform": "YouTube",
  "usage": "Thumbnail",
  "official": {                       // null when no official dimension was found
    "recommended": { "w": 3840, "h": 2160 },
    "min": { "w": 640 },
    "aspect_ratio": "16:9",
    "max_file_size": "2 MB (mobile upload) / 50MB (desktop upload)",
    "formats": ["JPG", "PNG"],
    "source": { "url": "https://support.google.com/youtube/answer/72431", "publisher": "YouTube Help (Google)", "quote": "…", "checked": "2026-11-08" }
  },
  "facts": [                          // processing, cropping, safeZone, uploadLimits
    { "type": "cropping", "text": "…", "source": { "url": "…", "quote": "…", "checked": "2026-10-24" } }
  ],
  "pixohub_preset": { "width": 1280, "height": 720, "aspect": "16:9", "matches_official": "partial" },
  "notes": "…",
  "tool": "https://pixohub.com/resize/youtube-thumbnail"
}

matches_official is true, "partial" (same ratio or inside a documented range, different pixels), false, or null (no official pixel value to compare).

upload-size-limits.json

organization, what, kind (email, government-exam, visa-passport, community-avatar, social, ecommerce, …), min_kb, max_kb, other_requirements, source {name, url, quote, checked}, tool (the largest Pixohub compress-to-size page that fits).

Usage

const res = await fetch("https://pixohub.com/open-data/platform-image-sizes.json");
const { items } = await res.json();
const story = items.find((i) => i.id === "instagram-story");

import json, urllib.request
data = json.load(urllib.request.urlopen("https://pixohub.com/open-data/upload-size-limits.json"))
print([l for l in data["items"] if "Gmail" in l["organization"]])

MCP server

The same data is queryable by AI assistants through a free, read-only MCP server (Streamable HTTP, no key):

https://mcp.pixohub.com/mcp

claude mcp add --transport http pixohub https://mcp.pixohub.com/mcp

Tools: get_platform_image_size, find_upload_size_limit, recommend_image_format, compression_advice, conversion_test_result.

Method and caveats

Official sources only. Help centres, developer docs, ads guides and standards text. Third-party "size guide" blogs are not used. Where an official page could not be read (blocked or client-rendered), the field is null rather than filled from elsewhere. Paper sizes whose only readable source was Wikipedia are left out of official.
Platforms change specs. Each fact carries the date it was checked; re-check the linked page before relying on a hard limit.
Measurements come from Pixohub's in-browser pipeline (Chromium via Playwright). Test photos are from Wikimedia Commons (licences listed in compression-tests.json) and the Kodak Lossless True Color Image Suite. Method: pixohub.com/editorial-policy.
Found an outdated value? Open an issue with the official link.

Licence

Compilation and measurements: CC BY 4.0 — credit "Pixohub (pixohub.com)" with a link. Quoted passages remain the property of their publishers and are included only to show where each fact comes from.

pixohub

Documentation