AI Thumbnail Generation

Generate high-resolution YouTube thumbnails using the Nano Banana AI engine

AI Thumbnail Generation

TubeLog's Nano Banana AI engine generates high-resolution thumbnails (1280×720) optimized for YouTube CTR. You can create multiple variations from a single prompt and A/B test them directly through TubeLog.

#Credit Cost

10 credits per generated image

#How to Generate a Thumbnail

  1. Go to Thumbnails → Generate tab
  2. Enter your video title (used to guide the AI)
  3. Write a thumbnail prompt describing the visual style
  4. Optionally upload a reference image for style matching
  5. Select the number of variations (1–4)
  6. Click Generate

Generation takes approximately 15–45 seconds per image.

#Writing Effective Prompts

The quality of your thumbnail depends heavily on the prompt. Here are guidelines:

#Good Prompt Structure

[Subject] + [Action/Expression] + [Background/Setting] + [Style/Mood]

Example:

A shocked creator pointing at a glowing YouTube analytics graph, dark studio background with neon blue lighting, dramatic cinematic style, high contrast

#Tips

  • Be specific about expressions — "shocked face", "big smile", "serious look" works better than "person"
  • Mention text placement — "bold white text at the bottom" guides the AI to leave space for overlays
  • Reference colors — Use your brand colors: "red and black color scheme"
  • Avoid copyrighted elements — Don't reference specific brand logos or celebrity likenesses

#Generation Models

| Model | Speed | Quality | Best For | |-------|-------|---------|---------| | Gemini 3 Pro | Medium | Highest | Final thumbnails, photorealistic | | Gemini 2.5 Flash | Fast | High | Batch generation, rapid iteration |

TubeLog selects the model based on your plan and queue load. Pro/Enterprise users can specify the model manually.

#After Generation

#Download

Click the Download button on any generated thumbnail to save the full 1280×720 PNG to your device.

#Upload to YouTube

  1. Select a generated thumbnail
  2. Click Set as Thumbnail
  3. Choose which video to apply it to
  4. TubeLog uploads it via YouTube Data API v3

#Run Analysis

After generating, click Analyze to run a TubeLog Score assessment on your new thumbnail before publishing it. This helps you pick the best variation.

#A/B Testing via Auto-Replacement

  1. Select two generated thumbnails
  2. Go to Auto-Replacement tab
  3. Set a test schedule (e.g., Thumbnail A for 48h → switch to Thumbnail B)
  4. Track CTR change in the replacement timeline

#Batch Generation (Pro / Enterprise)

Pro and Enterprise plans support batch generation:

  • Generate thumbnails for multiple videos simultaneously
  • Queue up to 20 generation jobs at once
  • Results saved to your thumbnail library

#Thumbnail Library

All generated thumbnails are saved to your Thumbnail Library in Cloudflare R2 storage. Access them anytime from the Thumbnails → Library tab.

  • Storage persists across sessions
  • Organized by channel and video
  • Thumbnails are retained for 90 days (Pro) or 1 year (Enterprise)