Complete reference tables covering every metadata field, character limit, and algorithm signal across YouTube, Etsy, Instagram, TikTok, Pinterest, Adobe Stock, Redbubble, Facebook, X, Amazon, and Shopify.
Last updated: April 17, 2026 · 11 platforms · 2,400+ words
No two platforms handle metadata the same way. YouTube treats tags as supplementary context while Etsy treats them as first-class search signals. Amazon demands structured bullet points and a hidden backend keyword field. Adobe Stock needs exactly the right keywords to pass editorial review. Instagram's algorithm weighs hashtags differently depending on whether you're a new or established account.
This reference page exists so you don't have to keep 11 browser tabs open. Everything is consolidated here: every field, every limit, what each algorithm actually indexes, and how much SEO weight each field carries. Bookmark it. Share it. Use it every time you publish to a new platform.
How to use this page: Start with the master comparison table for a quick overview, then scroll to the platform category sections for deeper guidance. The "What algorithms index" table is especially useful if you're deciding where to focus your optimization effort.
This table shows the primary metadata fields, hard character/count limits, secondary fields, what each algorithm actively indexes, and the relative SEO weight of each field type.
| Platform | Type | Primary Field | Limit | Secondary Fields | Algorithm Indexes | SEO Weight |
|---|---|---|---|---|---|---|
| YouTube | Title | 100 chars (show ~60–70) | Description (5,000 chars), Tags (500 chars total / up to 15 tags), Chapters, Cards | Title, first 200 chars of description, tags, closed captions, engagement signals | Very High | |
| Etsy | Marketplace | Listing Title | 140 chars | Tags (13 tags × 20 chars each = 260 chars), Description (no limit; first ~160 chars shown in search), Attributes, Materials | Title, all 13 tags, attributes, renewal recency, conversion rate, shipping speed | Very High |
| Caption | 2,200 chars (show ~125 before "more") | Hashtags (up to 30, counted within caption), Alt text (manual or auto), Location tag | Caption text, hashtags, alt text, engagement rate, save rate, share rate | Medium | ||
| TikTok | Caption | 2,200 chars including hashtags | Hashtags (embedded in caption), On-screen text, Audio metadata, Account niche signals | Caption + hashtags, audio track, video transcript (auto-captioning), watch time, completion rate | Medium–High | |
| Pin Title | 100 chars (show ~30–40 in feed) | Description (500 chars), Hashtags (up to 20, use 2–5 for best results), Board name, Alt text | Pin title, description keywords, board name, hashtags, link domain authority, save/repin rate | High | ||
| Adobe Stock | Stock | Title | 200 chars | Keywords (up to 50, comma-separated), Category (1 of 24 categories), Editorial flag | All keywords (equal weight), title, category, technical metadata (camera EXIF), license type | Very High |
| Redbubble | POD Marketplace | Title | 60 chars | Tags (up to 15 tags), Description (500 chars), Default product selection | Title, tags, description keywords, sales velocity, product type associations | Medium–High |
| Post Copy | 63,206 chars (effectively unlimited) | Hashtags (2–3 recommended), Link preview title/description, Alt text on images | Post text, engagement (reactions, comments, shares), video watch time, link preview metadata | Low (organic reach) | ||
| X (Twitter) | Tweet | 280 chars | Hashtags (0–2 recommended; too many reduce reach), Alt text on images, Thread context | Tweet text, engagement (retweets, replies, likes), hashtag topic clustering, link preview | Low | |
| Amazon | Marketplace | Product Title | 200 chars (category-dependent) | Bullet Points (5 × 200 chars), Backend Keywords (250 bytes, not visible to buyers), Description (2,000 chars), A+ Content | Title, bullet points, backend keywords, customer reviews, conversion rate, click-through rate, sales rank | Very High |
| Shopify | Ecommerce | Product Title | 255 chars | Description (no limit), Meta title (70 chars), Meta description (160 chars), Tags (for filtering), URL handle | Meta title, meta description, product title, description body, URL slug, Google Shopping feed data | High (Google SEO) |
Social platforms prioritize engagement signals over metadata structure. That said, metadata still sets the discovery context — the algorithm needs text signals to know who to show your content to before it can measure engagement.
YouTube is the second-largest search engine in the world, and its metadata system reflects that. The title is your most important field — it needs to include your primary keyword naturally within the first 60 characters. The description gives you 5,000 characters, but only the first 150–200 are shown before truncation in search results; front-load your keywords there. Tags serve as category context, not ranking factors — use them to reinforce your topic, correct likely misspellings, and cluster related concepts. YouTube also reads auto-generated captions, so clear spoken audio can effectively extend your keyword reach.
Instagram's metadata is caption-plus-hashtag based. The first line of your caption is the most visible real estate — it shows in feed before the "more" truncation. Hashtags function as topical signals that place your content into category feeds; the optimal number is debated but most creators see diminishing returns after 10–15. Instagram also allows you to add manual alt text on images, which is both an accessibility feature and an indexable text signal for the algorithm. Location tags add a geographic discovery layer.
TikTok's algorithm is unusually powerful at understanding video content directly — it reads on-screen text, transcribes audio, and analyzes visual content. Your caption (2,200 chars shared with hashtags) still matters for initial categorization, but watch time and completion rate are the dominant ranking signals. Use 3–5 highly specific hashtags rather than a pile of broad ones. The audio track is a metadata layer unique to TikTok: using trending sounds signals topical relevance to the algorithm.
Pinterest is the most SEO-like of all social platforms. Users search with intent, boards provide long-term ranking context, and pins age gracefully — a well-optimized pin can surface in searches years after publication. Your pin title (100 chars) is the highest-weight field. The description (500 chars) should read naturally but include 3–5 keyword phrases relevant to what people search. Hashtags on Pinterest work more like tags than on Instagram — use 2–5 targeted ones. Your board name provides important topical context for every pin inside it.
Marketplace platforms have the highest SEO stakes because metadata directly drives purchase-intent traffic. Poor metadata means invisible listings regardless of product quality.
Etsy search is driven primarily by the listing title and the 13 tags. Each tag can be up to 20 characters and can be a multi-word phrase — use all 13 every time. Etsy's algorithm (Cassini) matches shopper search queries against your title and tags first, then weighs conversion rate, shipping speed, and recency. The description is not heavily weighted for internal Etsy search, but the first 160 characters appear in Google search previews — treat it as your meta description. Attributes (color, size, occasion, style) add additional filter-based discoverability that many sellers ignore.
Amazon's A9/A10 algorithm is the most sophisticated of any marketplace. Your product title should include the brand, product type, key features, and variant — in that order — within 200 characters. The five bullet points are prime indexed real estate: lead each with a capitalized benefit keyword. The backend search terms field (250 bytes — bytes, not characters) accepts keywords that buyers never see but Amazon indexes; do not repeat terms already in your title or bullets. Conversion rate and click-through rate are powerful ranking factors — metadata sets the stage but performance data drives long-term rank.
Shopify metadata serves two audiences: your store's internal search and Google. For Google, the most important fields are the meta title (70 chars) and meta description (160 chars) in the SEO panel — these become your Google search snippet. The product title appears in page headings and Google Shopping feeds. Your URL handle should be keyword-rich and concise (e.g., /products/silver-hoop-earrings not /products/SKU-38472). Product tags in Shopify are used for internal collection filtering, not Google SEO.
Adobe Stock metadata is precise and unforgiving. Contributors with poor keyword quality face lower placement or rejection. Your title (200 chars) should describe the image naturally, as if explaining it to someone who can't see it — avoid keyword stuffing. Your keywords (up to 50) are all treated with approximately equal weight; order matters slightly for the first few terms, but quality matters more than stuffing all 50. Pick the category carefully — it's a hard filter that affects where your work surfaces in category-browse mode. Flag editorial content correctly or risk rejection.
Redbubble's internal search and Google Shopping both pick up your title, tags, and description. The 60-character title limit is strict — front-load your primary keyword phrase. Use all 15 tags, mixing specific descriptors (e.g., "black cat astronaut") with broader category terms (e.g., "funny cat shirt"). The description (500 chars) is indexed both by Redbubble and by Google, so write it for humans but include 2–3 keyword phrases naturally. Redbubble also tracks sales velocity per design, which affects placement in trending sections.
This table breaks down exactly which fields each platform's algorithm uses as ranking signals, separated into primary (strong weight) and secondary (moderate or contextual weight) signals.
| Platform | Primary Indexed Fields | Secondary Indexed Fields | NOT Indexed / Ignored |
|---|---|---|---|
| YouTube | Title, first ~200 chars of description, auto-captions, engagement rate | Tags, chapters, cards, end screens, watch time, CTR | Tags alone don't rank — they're contextual only. Long descriptions beyond 200 chars have minimal weight. |
| Etsy | Title, all 13 tags, attributes, conversion rate | Description (for Google, not Etsy), materials, shipping speed, recency | Description has no direct Etsy search weight. Duplicate tags reduce effectiveness. |
| Caption text, hashtags, engagement (saves, shares), account niche history | Alt text, location tag, mention tags, reel audio | Keyword density in captions doesn't improve ranking beyond relevance. Instagram doesn't index links. | |
| TikTok | Caption + hashtags, video transcript (auto-captions), watch time, completion rate | On-screen text, audio track, account niche signals, share rate | Links in captions are not clickable and not indexed. Keyword stuffing in captions can hurt reach. |
| Pin title, description keywords, board name | Hashtags (2–5), domain authority of linked URL, save/repin rate | Pin descriptions beyond 500 chars are truncated. Alt text helps accessibility but is a weak ranking signal. | |
| Adobe Stock | All keywords (equal weight), title, category selection | EXIF/IPTC metadata, editorial flag, contributor track record | Description is not searchable. Comments and internal notes are not indexed. |
| Amazon | Product title, bullet points, backend keywords, sales/conversion data | Description, A+ content, customer reviews (sentiment + keywords), Q&A | Backend keyword field has a strict 250-byte cap — exceeding it causes truncation and indexing issues. Repeating terms wastes byte space. |
| Shopify | Meta title, meta description, product title (Google Shopping), URL handle | Description body, product tags (internal filtering), image alt text | Shopify's internal search indexes product title and tags only. Google indexes everything in the HTML. |
These are the errors that consistently hurt discoverability, organized by platform.
| Platform | Common Mistake | Why It Hurts | Fix |
|---|---|---|---|
| YouTube | Putting the keyword at the end of the title | Truncated in search results; algorithm front-weights early words | Open with your primary keyword, then add context and intrigue |
| Etsy | Using fewer than 13 tags or repeating title words in tags | Wastes indexable keyword slots; Etsy already reads your title | Use all 13 tags with new keyword angles not in your title |
| Using 30 broad generic hashtags (#love, #instagood) | Content gets buried in high-volume feeds with zero engagement | Use 10–15 niche-specific hashtags matched to your actual content and audience size | |
| TikTok | Ignoring the caption entirely or using only 1–2 words | Algorithm has no text signal for initial distribution | Write a 1–2 sentence caption with 3–5 targeted hashtags |
| Using the same generic board name for everything ("My Pins") | Board name is a strong topical signal — generic names destroy category relevance | Create specific boards with keyword-rich names ("Minimalist Living Room Decor Ideas") | |
| Adobe Stock | Submitting AI-generated images without proper disclosure or keyword accuracy | Risk of rejection or removal; keywords for AI images must describe the actual content | Always tag AI-generated content accurately; follow Adobe's contributor guidelines |
| Amazon | Repeating the same keywords in title, bullets, AND backend field | Wastes the 250-byte backend field on already-indexed terms | Use backend field for synonyms, alternate spellings, and long-tail variations not in visible copy |
| Shopify | Leaving default meta title/description as the product title | Missing the chance to write Google-optimized snippet text; hurts CTR | Write a custom 60-char meta title and 155-char meta description for every key product |
| Redbubble | Using only 3–5 tags when 15 are allowed | Severely limits surface area in internal and Google search | Fill all 15 tags with a mix of specific and category-level terms |
| Using 10+ hashtags like Instagram | Facebook's algorithm de-prioritizes posts with excessive hashtags | Use 1–3 hashtags maximum; focus on post quality and shareability | |
| X (Twitter) | Using 3+ hashtags, especially broad trending ones | Looks spammy; X's algorithm penalizes hashtag overuse | Use 1–2 specific hashtags or none; let the text quality drive engagement |
Metadata Reactor provides dedicated AI metadata generators for all 11 platforms covered in this guide. Each tool is tuned to the specific field requirements, character limits, and algorithm expectations of its platform.