Creative formatting

Every form factor starts with your creative, or the content of your mail piece. Lob’s core technology is built around modern APIs that remove the typical complexities and limitations of the print and mail industry. We can accept static PDFs, but similar to email sends, HTML enables dynamic personalization so each and every mail piece is unique.

Example pieces

See Lob's Template Gallery for pre-designed templates to help you get started. You can fork these to create your own designs.

File formats

HTML for dynamic creatives

We highly recommend designing your direct mail in HTML, as opposed to static formats. The flexibility afforded by HTML includes the incorporation of dynamic merge variables into the design, which enables sending personalized content at scale. See dynamic personalization for more information.

  • When designing content with HTML, use inline styles or an internal stylesheet. Do not use an external stylesheet.

  • If you are linking to images, please ensure that they are at least 300 dpi (but there is no need to go higher than 300 dpi). Because the content is only being designed for a single size, we recommend using absolute positioning, as shown below.

body {
  width: 6.25in;
  height: 4.25in;
  margin: 0;
  padding: 0;
  background-image: url(;
  background-size: 6.25in 4.25in;
  background-repeat: no-repeat;

#safe-area {
  position: absolute;
  width: 5.875in;
  height: 3.875in;
  left: 0.1875in;
  top: 0.1875in;
  background-color: rgba(255,255,255,0.5);

PDFs for static creatives

Lob processes and prints various types of PDFs, however, we ask that you follow our PDF formatting guidelines outlined in our PDF preflight checklist to help ensure successful and accurate printing. If you use Adobe InDesign to create PDFs for Lob, you can also reference the video Exporting PDFs from InDesign to audit your creative before it is sent to Lob.

Font formats

Supported fonts

Ideally, all fonts in provided PDFs should be embedded. Embedding a font in a PDF ensures that the final printed product will look as it was designed. Fonts can vary greatly in size and shape, even within the same family. If the exact font that was used to design the artwork is not used to print, the look and placement of the text is not guaranteed to be the same.

In general, requests that provide PDFs with un-embedded fonts will be rejected. We make an exception for "standard fonts", a set of fonts that we have identified as being common. PDFs that contain un-embedded fonts that are found in the list, and match the accepted font type will be accepted. Otherwise, the request will be rejected.

We support the following web font formats:

  • TTF

  • OTF

  • SVG

  • EOT

  • Google web fonts

  • Custom fonts within your HTML templates

  • See our full list of supported PDF Fonts in our API docs

Unsupported fonts

  • Type 1 fonts (deprecated Jan 2023)

  • Type 3 fonts

  • Adobe (Typekit) fonts Adobe Fonts (formerly Typekit Fonts): These fonts require white-listing a specific domain, which Lob is unable to do. Our recommendation is to either host the font yourself and use it within your HTML, or find an appropriate non-Typekit font to replace it with.

Image formats

When using PNGs or JPEGs with Lob, we require a minimum of 300 dpi. The dpi is calculated as (width of image in pixels) / (width of product in inches) and (length of image in pixels) / (length of product in inches). For example: 1275px x 1875px image used to create a 4.25" x 6.25" postcard has a dpi of 300. It is also recommended that you don't greatly exceed 300 dpi, as this will result in unnecessary additional file size.

Submitted images must have the same length-to-width ratio as the chosen product. Images will not be cropped or stretched by the API.


This is a raster image format that can have a transparent background. It is generally of higher quality than other image formats.


This is a raster image format that is often used for photographs. It does not allow for a transparent background.

Hosting content

When you pass an image or send HTML in your API request, Lob will then render and host the content. If you are sending at high volumes, we recommend you host the content yourself on a performant file hosting provider, such as Amazon S3, and send Lob a hosting URL to the content in your API request. This will reduce your API request time.

Rendering best practices

To see how your HTML is rendered, create a Test API request either through the API or view a preview in the dashboard (HTML templates). If using Campaigns UI, you will be presented with a creative proof of a single mail piece.

This works for PDFs as well as long as the submitted PDF follows our guidelines. If a PDF not following guidelines is submitted, the rendered proof may not reflect the final printed product.

See here if you are experiencing rendering errors.

We highly recommend sending yourself a printed piece to validate the mail piece's appearance.

Recommended tools


Lob's HTML renderer is based on Webkit. For this reason, using the Safari browser will show previews more accurately. For the best results, we recommend submitting test API requests and reviewing the rendered PDF.


We highly recommend using the Adobe Creative Suite (Adobe Illustrator, Photoshop, or InDesign) to design your content. This will give you design flexibility and multiple export options. Here are some tips to create print-ready PDFs with InDesign.

Please note that PNG files are RGB only—to prepare a file for printing, our rendering engine must convert this color profile to CMYK. During this conversion, there may be a slight variance in color that would impact the print result. If you have a need for a specific color experience (to abide by brand guidelines for example), then we recommend providing a PDF file and/or evaluating the color in Adobe Photoshop Pro.

Converting from PDF to HTML

We recommend using a developer to convert your PDF designs to HTML. We'd estimate 15 minutes to 2 hours of development time for the average file. Some applications like Adobe Illustrator come with HTML export options, but note that their exports won't typically produce HTML that conforms to Lob's requirements.

Need help with converting your creative files to HTML? You can now easily import your creative from popular design programs and quickly spin up merge variables. See Creative conversion tools for more info.

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