How to Prepare Substack Images Before Publishing a Newsletter
When an educator, analyst, or small media brand prepares a Substack post image, the safest workflow is not to upload the biggest available file and hope the editor handles it. Define the image role, keep the source file, create a role-specific delivery copy, preview it in email and web layouts, then publish only after crop, readability, and load feel are acceptable.
This step-by-step workflow works for publication logos, cover images, preview images, article headers, charts, screenshots, GIFs, and inline editorial images.
Step 1: Decide the image role
Start by naming the role: logo, cover image, social/post preview image, article header, chart, screenshot, animated GIF, or inline image. That one decision controls the crop, file format, and preview checks. A logo needs identity at small sizes. A chart needs readable labels. A preview image needs a clear centered focal point.
Step 2: Keep the original unchanged
Save the original photo, design, chart export, or screenshot before editing. The published file should be a delivery copy. If the preview crops badly or compression damages text, you can rebuild from the clean source instead of trying to repair a damaged upload copy.
Step 3: Choose the canvas or crop
Use the role to choose a starting canvas. Substack recommends at least 1200 x 630 pixels for social or post preview images, at least 600 x 600 pixels for cover images, at least 256 x 256 pixels for logos, and around 1100 x 220 pixels for email banners. For body images, crop based on what the reader needs to understand in the email or web post.
Step 4: Keep the focal point mobile-safe
Place the subject near the center, simplify the background, and avoid important details along the edges. If the image will be used as a preview card, assume some surfaces may crop differently. A simple focal point survives better than a dense collage.
Step 5: Avoid tiny text inside the image
Charts, screenshots, and quote graphics should use larger labels than you would use in a desktop report. Put essential explanations in the article body too. If the image contains a chart, make the title, legend, axis labels, and key annotation readable on a phone-width preview.
Step 6: Export as JPG, PNG, or GIF
Use JPG for photo-like editorial images. Use PNG for screenshots, charts, diagrams, and text-heavy graphics. Use GIF only when a short motion explains something that a still image cannot. If the GIF is long or full-screen, consider a static image instead.
Step 7: Compress a delivery copy carefully
Compression should make the upload copy lighter without damaging the point of the image. Compare the delivery copy with the source at the size readers will see. If screenshot text looks fuzzy or chart labels break apart, use less compression, switch to PNG, or simplify the image.
Step 8: Upload to Substack and preview the post
Upload the image into the relevant Substack surface. In the post editor, Substack provides image controls such as full-width display, crop, caption, link, watermark, and alt text editing. Use these controls deliberately, then preview the full post rather than judging the image only inside the editor.
Step 9: Check email, web, mobile, and social preview behavior
Preview the email layout, web post, mobile reading width, and social/post preview image. Look for awkward crop, slow-feeling image load, weak contrast, small embedded text, and images that crowd the first screen. If the image fails one important surface, rebuild the delivery copy for that role.
Step 10: Save source files for future updates
Keep the source design, original chart, editable graphic, or uncropped photo in your own files. Newsletter visuals often need updates when a brand changes, a chart is revised, or a tutorial screenshot becomes outdated. A clean source makes future updates faster and safer.
Substack pre-send checklist
| Substack surface | Image to verify | Reader risk | Pass condition |
|---|---|---|---|
| Email body | Inline chart, screenshot, or editorial image | The email feels slow or the image crowds the first screen. | The image loads cleanly and supports the paragraph around it. |
| Mobile reading view | Charts, screenshots, and text-heavy graphics | Labels become too small to read without zooming. | The main point remains readable at phone width. |
| Web post | Header and post body images | The image looks oversized compared with the article layout. | The crop feels intentional and does not interrupt reading. |
| Social preview | Preview image or post thumbnail | The crop hides the subject or edge text. | The focal point remains visible in the preview card. |
| Publication branding | Logo, cover image, and banner | Brand assets look inconsistent or soft. | Each branding image uses a role-specific export. |
FAQs
Prepare the delivery copy before upload, then use Substack's preview and image controls to confirm the crop, width, caption, and alt text.
Check the image role, crop, focal point, mobile readability, format, compression quality, email preview, web post preview, and social preview crop.
The uploaded copy is usually optimized for one delivery role. Keeping the source lets you rebuild the image later if the brand, chart, screenshot, or post format changes.
