Send title and issue metadata as JSON, get back a 1200x300 PNG sized for email banners.
Newsletter publishers and transactional email systems use the email header image generator to ship per-issue banner art that fits cleanly inside Mailchimp, ConvertKit, Brevo, and other ESP templates. The 4:1 ratio matches the wide banner slot most email tools expose at the top of the body, and the layout adapts to issue numbers, dates, and brand logos. You post the title, optional issue number, and brand inputs as JSON, and the response holds a PNG ready to drop into your campaign builder.
curl -X POST https://app.html2img.com/api/v1/templates/email-header \
-H "X-API-Key: YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"title":"The Production Hour Weekly","subtitle":"Conversations from the people running real systems","issue_number":"Issue #042","publication_date":"May 6, 2026","background_pattern":"dots","accent_color":"#7C3AED","background_color":"#0F172A"}'A single cURL call to render a Email Header as a PNG. For the full PHP, Node and Python equivalents, plus every input the template accepts, see the Email Header API reference. Setting up your key is covered in the authentication guide.
View the Email Header API reference — inputs, defaults, error responses and cURL, PHP, Node and Python code samples. Read the docs.
Newsletter operators sending weekly issues benefit from a unique banner per issue rather than reusing one stock graphic. Render with the issue number, headline topic, and accent_color from your brand kit, attach the URL to the campaign template, and each issue ships with fresh artwork. The Production Hour Weekly automates this through a script that runs on Tuesday mornings and produces 52 unique banners a year.
Welcome emails, password resets, and receipts benefit from banners that match the message intent rather than reusing a marketing banner. Render variants with type-specific copy ("Welcome", "Reset your password", "Your receipt") and the message reads as deliberate transactional design rather than recycled marketing. Halberd Software ships 8 transactional types through this template across its product flows.
Holiday and seasonal campaigns benefit from banners that reflect the season without redesigning the entire email template. Render with the campaign theme as the title and a seasonal accent_color, attach to the existing template body, and the email reads as season-appropriate without designer involvement. Riverside Bakery ships 12 seasonal campaign banners per year through this exact pattern.
Partner programs that send joint emails benefit from banners that carry both brand marks. Render with two logo URLs combined or with a partnership-specific accent_color, attach to the joint email template, and both partners ship co-branded artwork that reads as intentional collaboration. Linden & Co's 14 partner programs use this for monthly co-marketing pushes.
Internal newsletters from leadership, HR, or operations benefit from banners that distinguish the source. Render with the team or department name as the title and a department accent_color, attach to internal email templates, and employees can identify the source at a glance. Wren Analytics ships internal updates from 6 departments through this template, with consistent color-coding across the org.
Matches the spec at 4:1 landscape banner for ESP body templates.
POST to the template endpoint with the values you want rendered. Authenticate with your API key.
The template is rendered server-side as a 1200x300 PNG.
Cache it, embed it in your page, attach it to an email.
A banner designed for a white email body background can break in dark mode when the client inverts surrounding colors. Test in Gmail dark mode and Outlook dark mode, and use a transparent background with dark-mode-safe text colors so the banner adapts to either viewing surface.
Email clients on retina displays render images at 2x physical pixels. A 1x banner at 1200x300 looks soft on these screens. Render at 2x DPI by setting dpi=2 on the underlying API for retina-clean results, and the file size still stays manageable.
Mobile email scales the email body to fit a single column, which can compress a wide title to unreadable size. Keep titles under 50 characters or test in your top three email clients before scheduling a campaign that depends on the title being legible.
A quick summary of what the Email Header template accepts. The full reference, with example values and array shapes, is in the docs.
| Name | Type | Required |
|---|---|---|
title | string | Required |
subtitle | string | Optional |
issue_number | string | Optional |
publication_date | string | Optional |
background_pattern | enum | Optional |
accent_color | string | Optional |
background_color | string | Optional |
brand_logo_url | url | Optional |
See the full inputs reference for descriptions, examples and validation rules.
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A starting point from each of the other two template categories.
See the full template gallery for every design grouped by category.
What size suits most email tools?
The 1200x300 output (4:1 ratio) fits Mailchimp, ConvertKit, Brevo, Klaviyo, and most ESPs at full email body width. The banner scales down responsively in mobile clients to fit the single-column layout. File sizes between 30 KB and 100 KB are well below ESP caps.
Will it look right in dark mode?
Use a transparent background with dark-mode-safe colors so the banner adapts to whichever surface the user is viewing. Some email clients invert images entirely in dark mode, so test in Gmail and Outlook dark themes before going live with a campaign.
Can I generate one per newsletter issue?
Yes, call the endpoint per issue with the new title, issue_number, and publication_date. The render finishes in 1 to 2 seconds, and the URL drops into your campaign template. Most newsletter ops automate this through a webhook from their CMS.
Does it support retina rendering?
Yes, the rendered PNG is sharp at default 1x. For retina screens, set dpi=2 on the underlying API and the renderer produces a 2400x600 PNG that displays cleanly on high-density displays. The file size roughly triples but stays under the cap of every major ESP.
Can I include a CTA button?
No, the template does not render a CTA button. Buttons belong in the email body HTML rather than baked into an image, since image-only buttons hurt accessibility for screen readers and cannot be tracked the same way as anchor tags. Add the CTA in the email body below the banner.
What about transactional emails?
Yes, swap the title to match the message type ("Welcome", "Your receipt", "Password reset") and reuse across templates. Most transactional ESPs (Postmark, Resend) accept remote PNG URLs in the email body, so the same banner can serve every transactional template type.
25 renders a month on the free tier. See the pricing page for higher-volume plans.