Youtube Banner Spec

---
name: youtube-banner-spec
description: Technical specification for a YouTube banner — 2560x1440 and the mobile safe zone. Triggered when generating, reviewing or diagnosing a channel banner.
---

# Banner specification

## WHEN

Any banner generation or review. Load it **before** writing the prompt: the
safe zone cannot be fixed afterwards.

## THE RULE THAT DECIDES EVERYTHING

The banner is uploaded at **2560x1440**, but **on mobile only a narrow
horizontal strip across the vertical centre is visible**. The top and bottom
thirds are cropped away entirely.

Everything that matters — text, logo, channel name, faces, branding — goes
**inside that centre band**. Above and below, only simple backgrounds:
gradients, blurs, patterns, flat colour.

A banner that puts the channel name at the top disappears on mobile. It is the
most frequent failure and the most invisible one from a desktop.

## EXECUTION ORDER

1. **See the current banner before replacing it**
   `python3 tools/view_channel_packaging.py --only banner --md`
   and open the file.

2. **Generate with the right type**
   ```
   python3 tools/generate_image.py --type banner --prompt "..." --dry-run --md
   ```
   `--type banner` prepends the critical composition rule with the safe band.
   Check it in the dry run: if that clause is not in the final prompt,
   something is wrong with the configuration.

3. **Verify the result by opening it** and checking, specifically, that with
   the top and bottom thirds covered you can still tell what the channel is
   about.

4. **Adjust dimensions without regenerating**
   `python3 tools/export_image.py --image PATH --type banner`
   Leaves it at exactly 2560x1440. The crop is centred, so if the subject is
   off-centre you need to check it.

## STYLE

- Large, legible text; the banner is seen small on mobile.
- Branding centred, inside the band.
- The channel's palette, for consistency with the avatar. Load
  `analyse-channel-packaging` if you do not know it.

## SOURCES

The image is `source: generated`. The dimensions after `export_image` are
`derived` and verifiable in the file.

## OUTPUT

1. The banner file at exactly 2560x1440, opened and checked.
2. Confirmation that everything important sits inside the centre band, checked
   with the top and bottom thirds covered.
3. The model that generated it, named explicitly.