Nostr Photo Resizer

The Nostr Photo Resizer is a free online image resizer built for the Nostr protocol. It crops and resizes your pictures to the correct dimensions for profile photos (avatars), banner images, and note attachments so your posts render cleanly across every major Nostr client. Upload a JPG, PNG, WEBP, or GIF, pick a placement, and download an optimized file in seconds. No signup, no watermark, no Nostr account required.

Nostr is a decentralized social protocol where the same profile is rendered by many different clients (Damus, Amethyst, Primal, Iris, Snort, Nostur, and others). Each client crops avatars and banners a little differently, so a single oversized photo can look stretched on one app and cropped awkwardly on another. This resizer gives you a predictable, cross-client-friendly image every time.

Current Nostr image specs by placement

Nostr does not enforce fixed image dimensions at the protocol level. Instead, each client applies its own rendering rules on top of the picture and banner fields in your kind 0 metadata event. The dimensions below are the widely used safe sizes that look good across the major Nostr clients.

Profile photo (avatar) — Damus, Amethyst, Primal, Iris, Snort

• Recommended size: 400 x 400 pixels, square, 1:1 aspect ratio.
• Minimum safe size: 200 x 200 pixels so the avatar still looks crisp on retina and high-DPI screens.
• Maximum practical size: 1000 x 1000 pixels. Anything larger just inflates file size without improving display quality.
• Display shape: Damus, Primal, Iris, Snort, and Amethyst all crop the avatar into a circle, so keep the face or logo centered with safe padding on every edge.
• Format tip: JPG or WEBP for photos, PNG for logos or transparent marks.

Banner image — profile header

• Recommended size: 1500 x 500 pixels, 3:1 aspect ratio.
• Alternative size: 1200 x 400 pixels if you want a smaller file while keeping the same ratio.
• Mobile crop behavior: Damus and Primal show a shorter band of the banner on phones, so keep text and faces roughly centered vertically and avoid important details in the top and bottom 15 percent.
• Safe zone: Place logos, usernames, and slogans inside the middle 60 percent of the image so clients that crop more aggressively still show them.

Note attachments (images posted inside notes)

• Recommended longest edge: 1080 to 1600 pixels. This is large enough for clear zoom on mobile and desktop without making relays reject oversized uploads.
• Common aspect ratios: 1:1 (square), 4:5 (portrait), 16:9 (landscape). Square and 4:5 tend to get the most vertical space in feeds.
• File size target: Keep each attached image under about 1 MB. Many NIP-96 and Blossom media hosts used by Nostr clients apply their own per-file size limits.
• Animated GIFs: Supported by most clients, but convert long loops to short WEBP or MP4 when possible for faster loading.

What the Nostr Photo Resizer does

The tool does three jobs in one step:

• Resize your image to the exact pixel dimensions recommended for Nostr avatars, banners, or note attachments.
• Crop to the right aspect ratio (1:1 for avatars, 3:1 for banners, or a custom ratio for notes) so nothing important is cut off.
• Compress the output so the final file is small enough to upload comfortably to any Nostr media host without losing visible quality.

Everything runs from your browser. You do not need Photoshop, Figma, or any desktop app. The resizer is free for unlimited use.

Supported formats

• JPG / JPEG — best for photos of people, landscapes, and anything with smooth color gradients.
• PNG — best for logos, avatars with transparent backgrounds, and flat illustrations.
• WEBP — modern format with excellent compression; supported by all current Nostr clients and browsers.
• GIF — useful for short animated avatars and reaction images inside notes.

How to use the Nostr Photo Resizer

• Step 1: Upload your image by dragging it into the drop zone or clicking to browse.
• Step 2: Choose the placement — profile photo, banner image, or note attachment.
• Step 3: Adjust the crop box so the focal point (your face, logo, or headline) sits in the middle.
• Step 4: Pick your export format (JPG, PNG, WEBP, or GIF).
• Step 5: Click Download and save the resized file.
• Step 6: Upload the file to your Nostr client or media host, then update your kind 0 profile event or attach it to a note.

Best practices for Nostr images

Design for cross-client compatibility

Because every Nostr client (Damus, Amethyst, Primal, Iris, Snort, Nostur, Coracle, and others) decides how to render an avatar or banner, your image should look acceptable under the strictest cropping rule. Keep avatars centered and square, keep banner text inside the middle safe zone, and avoid tiny details that disappear when a client shrinks the thumbnail.

Follow NIP-94 and NIP-96 media conventions

NIP-94 describes how file metadata (dimensions, MIME type, hash, alt text) is attached to a Nostr event, and NIP-96 defines HTTP file storage servers that many clients use for media uploads. Uploading a correctly sized image means the width and height reported in your NIP-94 tags match what viewers actually see, which helps clients lay out the feed without layout shift.

Keep file sizes friendly to relays and hosts

Relays propagate your events, but the actual image bytes live on a media host. Large files take longer to upload, cost more for self-hosted media servers, and may be rejected by free hosts. Aim for under 200 KB for avatars, under 500 KB for banners, and under 1 MB for note attachments. The resizer compresses automatically to help you stay inside these limits.

Use alt text

Many Nostr clients support alt text for attached images through NIP-92 style tags. Describe the image in a short sentence so accessibility tools and low-bandwidth users still get the context.

Frequently asked questions

Is the Nostr Photo Resizer free?

Yes. The tool is completely free, with no watermark, no signup, and no upload limit.

Do I need a Nostr account or an npub to use it?

No. The resizer is a standalone image tool. You can use it before you even create a Nostr key pair.

Which size should I pick for my Nostr avatar?

400 x 400 pixels is the safe default for every major Nostr client. If you want extra sharpness on high-DPI displays, export at 800 x 800 pixels.

Which size should I pick for my Nostr banner?

1500 x 500 pixels (3:1 ratio) works well across Damus, Primal, Iris, Snort, and Amethyst. Keep important details centered so mobile crops do not hide them.

Will my resized image work on every Nostr client?

Yes. Nostr clients read the same picture and banner URLs from your kind 0 event, so a single correctly sized file is displayed by every client you log into.

Does the tool keep a copy of my image?

No. Images are processed for the resize and then discarded. Nothing is stored or shared.

Can I use the same image as my avatar on other networks?

Yes. A 400 x 400 square avatar also works for most other social profiles, so you can keep your identity consistent across Nostr and traditional platforms.

Publish to Nostr and everywhere else with Postiz

Once your images are sized correctly, you still need a calm way to post them on a schedule. Postiz is an open-source social media scheduler that lets you plan, queue, and publish content across Nostr and the rest of your social accounts from one clean calendar. Draft a note once, attach your freshly resized photo, and Postiz handles the timing, the repeat posts, and the analytics. Try Postiz for free and turn your Nostr presence into a consistent, low-effort routine.