# Puffles Studio > Puffles Studio is a free NFT collection generator that runs in your browser. You import folders of trait layer images, set rarity and rules, preview, and download one ZIP of images plus OpenSea-style metadata, made on your device or in a free cloud build. It does not mint, deploy contracts or host files. Key facts: - Free: no subscription, export fee, per-NFT fee or watermark. Outside hosting and minting services may charge their own fees. - Using the studio needs a sign-in with an email or a wallet (Privy): no password, no fee, and no wallet needed. The starter playground on the home page and the Creatives page need no sign-in. - Up to 20,000 NFTs per collection, 1 of 1s included. - Input: one folder per trait type, holding PNG, JPG or WebP images of up to 50 MB and 8,192 px on either side. Up to 10,000 trait images per import, 64 layers, 2,000 traits per layer, 5,000 rules and 2,000 1 of 1s. - Rarity by weight or by exact count. A #N at the end of a file name sets the starting weight (Crown#5.png is "Crown" with weight 5; the default is 1). Weights become exact whole-number counts that always add up to the collection size. Optional "None" choices, never-together rules, and 1 of 1s placed throughout or at the end. - It counts how many different pictures the traits can make and checks that every NFT looks different, including traits that hide others. - The same traits, layer order, rules, counts and seed always give the same collection. - Output: PNG or JPEG, at any width from 64 to 8,192 px or the original size. One ZIP holding images/, json/ (one file per NFT), _metadata.json, rarity.csv, opensea_Metadata.csv (for an OpenSea drop), nft-generator.json (the settings) and README.txt. File numbers and name numbers each start at any whole number from 0 to 1,000,000. - Metadata is EVM/OpenSea-style: name, description (if you wrote one), image and attributes. Images are PNG or JPEG only. - The images-folder address (ipfs://, https:// or ar://) goes into the metadata from the studio's Metadata settings, or later from My collections ("Update metadata in a finished export"). After a cloud build it is set on the build page, which gives -updated-metadata.zip. Until then the metadata carries the placeholder ipfs://REPLACE_WITH_IMAGES_CID. - Build on this device: nothing is uploaded, a ZIP made in memory can be up to 512 MB, and supported browsers can write straight to disk. Build in the cloud (free, up to 10,000 NFTs from trait images of up to 4,096 px; the export step shows the current limits): the upload picks up where it stopped, the tab can be closed once it is done, and you get one ZIP in the same layout plus a private link that anyone holding it can open. Cloud files are deleted after a few days. - Collections are saved in your browser, and you can download a project backup. No ad trackers and no analytics of its own. ## Docs - [How it works](https://puffles.io/guide): folder layout, rarity, rules, 1 of 1s, preview, export, cloud builds and the images-folder address - [Questions and answers](https://puffles.io/guide#faq): price, sign-in, privacy, what the export holds, size limits - [Learn](https://puffles.io/learn): every guide below, on one page - [About](https://puffles.io/about) ## Learn - [How Many Traits Do You Need for 10,000 NFTs? The Real Maths](https://puffles.io/learn/how-many-traits-for-10000-nfts): Multiplying trait counts is only the start. See how rules, None choices, exact counts and traits that hide others change how many different NFTs you can make. - [OpenSea Drop Metadata CSV: Columns, Rules and a Free Maker](https://puffles.io/learn/opensea-drop-metadata-csv): The columns OpenSea's drop CSV needs (tokenID, name, file_name, attributes), the rules it checks, and how to get the file made for you instead of by hand. - [How to Add 1 of 1s to a Generative NFT Collection](https://puffles.io/learn/add-1-of-1s-to-generative-collection): Add hand-made 1 of 1 artworks to a generated NFT collection: how they count toward the total, random or end placement, and what their metadata looks like. - [Free NFT Generators Compared (2026): Real Prices, Limits](https://puffles.io/learn/free-nft-generators-compared): What free really means at TheMintLab, Genfty, NFTGen, Bueno, OneMint, NFT-Inator, HashLips and Puffles Studio: prices, size limits and sign-in, all sourced. - [OpenSea NFT Metadata Format Explained, With a Real Example](https://puffles.io/learn/opensea-metadata-format): What each field in an OpenSea-style NFT metadata file means (name, description, image, attributes), shown on a real generated file, with numbering and images. - [How to Make a 10,000 NFT Collection, Step by Step, Free](https://puffles.io/learn/make-10000-nft-collection): From trait folders to a finished ZIP of 10,000 images and metadata in Puffles Studio: import, rarity, rules, preview, a device or cloud build, then the address. - [How to Prepare NFT Trait Layers: Sizes, Transparency, Names](https://puffles.io/learn/prepare-nft-trait-layers): Get your art ready for a generator: one folder per trait type, one canvas size, transparent PNGs, layer order, #weights in file names and a 1 of 1 folder. - [NFT Trait Rarity for Creators: Weights, Exact Counts, None](https://puffles.io/learn/nft-rarity-for-creators): How to plan trait rarity when you make an NFT collection: how weights become counts, when to use an exact count, what None does, and how to read rarity.csv. - [Set Your NFT Image Address: IPFS, Arweave or HTTPS Metadata](https://puffles.io/learn/nft-image-address-ipfs-metadata): After you upload your images, put the folder's ipfs://, ar:// or https:// address into your NFT metadata and download it again, without changing a single image. ## Optional - [Creatives](https://puffles.io/creatives): collection sheets, social posts, banners and stories as PNGs, with no sign-in - [Brand kit](https://puffles.io/brand) - [Privacy policy](https://puffles.io/privacy) - [Terms of service](https://puffles.io/terms) - [The full text of the guide and every article](https://puffles.io/llms-full.txt)