How to bulk upload NFTs to OpenSea? (Collection management)

Preparing Your NFT Assets

1. Ensure each NFT has a unique, properly formatted image file—PNG, JPG, or GIF—with consistent dimensions and naming convention like 001.png, 002.png.

2. Create a corresponding JSON metadata file for every asset, including required fields such as name, description, and image (URL pointing to the hosted image).

3. Host all images and JSON files on a decentralized or reliable centralized service—IPFS via Pinata or Filebase is strongly recommended for permanence and OpenSea compatibility.

4. Verify that filenames in metadata match exactly with uploaded assets, including case sensitivity and extension.

5. Double-check file sizes: images under 10MB, JSON under 1MB, and avoid special characters or spaces in filenames.

Setting Up the Collection on OpenSea

1. Log into your OpenSea account using a wallet connected to the target network—Ethereum, Polygon, or Base—and navigate to My Collections.

2. Click Create a collection, fill in the name, description, category, and royalty settings—note that royalties are enforced only on certain chains and may be ignored post-deployment on others.

3. Upload a high-resolution banner and profile image; these affect visibility and credibility but do not impact minting functionality.

4. Select the correct blockchain and payment tokens accepted—this choice locks the collection’s contract environment and cannot be changed later.

5. Confirm creation and wait for the collection to appear in your dashboard before proceeding to bulk upload.

Using OpenSea’s Bulk Minting Interface

1. From your collection page, click Add item, then choose Import from file to initiate bulk upload.

2. Prepare a CSV file with columns matching OpenSea’s schema: name, description, external_link, image_url, animation_url, and attributes in JSON array format.

3. Each row corresponds to one NFT; ensure image_url resolves publicly and returns HTTP 200—broken links cause silent failures during processing.

4. Upload the CSV and confirm the preview matches expectations—OpenSea displays up to 10 sample rows before final submission.

5. Initiate the import; depending on size, this may take minutes to hours, and status updates appear under Activity in your collection view.

Handling Post-Upload Validation

1. Monitor the Activity tab for success or failure indicators—failed items show error codes like 400 Bad Request or 429 Rate Limited.

2. For failed uploads, cross-reference the CSV row number with OpenSea’s error log snippet and re-submit corrected entries individually if needed.

3. Confirm on-chain presence by checking the token ID on Etherscan or Polygonscan using the collection’s contract address and verifying the ownerOf() call returns your wallet.

4. Test listing one NFT manually to verify pricing, blockchain confirmation time, and visibility in search results before scaling listings.

5. Avoid triggering rate limits by spacing bulk operations across sessions—OpenSea throttles repeated API-style actions from the same IP or wallet within short intervals.

Frequently Asked Questions

Q: Can I change the blockchain of an existing collection after bulk upload?No. The chain is immutable once the collection is created. Migrating requires deploying a new collection and re-uploading all assets.

Q: Why do some NFTs show “Not yet minted” even after successful CSV import?This indicates lazy minting—assets exist off-chain until the first sale or explicit mint transaction. They remain visible but lack on-chain token IDs until finalized.

Q: Does OpenSea support animated 3D models like GLB in bulk uploads?Yes, if referenced correctly in the animation_url field and hosted on a CORS-enabled endpoint. GLB, MP4, and WEBM are accepted formats.

Q: Are traits and properties editable after bulk upload?Metadata is editable only if the collection uses a mutable standard like ERC-1155 with updatable URI. ERC-721 collections with immutable contracts lock attributes permanently after deployment.