Lob Help Center

Mail piece design formats

Anatomy of a mailpiece

When you send an API request to Lob, you are sending 3 pieces of information: 

  1. the "To" address, 
  2. the "From" address, and 
  3. the content.

Below are some best practices to follow when designing content for Lob.

Note: all measurements are in inches, denoted by the double prime symbol (e.g. 4" x 6").

Artboard components

Bleed area

In the above postcard, you'll notice that the file that you are sending to Lob is actually 4.25" x 6.25" instead of 4" x 6". This extra space is what we call the Bleed Area. The Bleed Area is included to ensure that artwork gets printed to the edge. The artwork gets printed with slightly larger dimensions than the actual card and is subsequently trimmed down in production. Backgrounds and graphics should be extended into the Bleed Area. If they don't extend into the Bleed Area, it can result in a white or unprinted border on the edge of the postcard.

There is no need to include crop marks in your submitted content.

Trim zone

The Trim Zone captures the finished size of a mail piece, which will result from the printer trimming down a larger sheet of paper. Artwork that extends into the Bleed Area will be trimmed down to the size of the actual mail piece.

Safe zone

Keep all critical text and artwork within 1/8" from the edge of the final size to ensure no important content is ever trimmed off.

Mail piece size

The sizes of our mail pieces and their respective print layout requirements can be found in each respective section in the Help Center. Note that the API will return an error if you input a non-HTML file with the incorrect dimensions.

No-ink zones

Address block & postage

On our postcards and self-mailer specs, there is a space marked as *RED: INK-FREE AREA* on the backside of the mail piece. Anything in this area will not be printed, as this space is where the postage and address information will be printed during the production process. Address blocks for 4" x 6" postcards measure 2.375" x 3.2835", and all other postcard and self-mailer blocks measure 2.375" x 4.0".

On letters, the address block is 3.15" x 2" large and is located 0.6" from the left edge and 0.84" from the top edge. A white box will be printed, upon which will be printed the address and barcode information. Any content in this area will be covered and will not be visible.  

On checks, the check itself will be printed at the 8.5" x 3.625" area at the top. This area must thus be left blank. Anything printed in this area will not be printed to leave room for check details, including address information, payment amount, signature, and bank routing numbers. All text and important information should be included within the safe zone of the check bottom or check attachment pages.

Eco-conscious certification 

Lob has partnered with USPS to include an eco-conscious certification to help customers demonstrate to their end-recipients that they are sending mail in an environmentally responsible way.

The eco-conscious certification will automatically be included within the official use address block of all mailers that are printed by Lob. This currently applies to postcards, self-mailers, and letters, but support of this certification will be expanded to other mail types printed by Lob in the future. It will not impact your workflow or the way you design your creatives in any way.

The certification measures 0.349" x 0.349", and is printed in either full color or black and white, depending on the letter settings. Address block placement and measurements for applicable formats can be found below. The certification is not included on Certified letters or letter templates for custom envelopes. You will be able to see the eco-conscious logo in the proof PDF after the order is submitted, which can be viewed from the Lob dashboard under your order.

Placement on postcards & self-mailers

On postcards or self-mailers, the eco-conscious certification will be placed between the return address, postage indicia, and IMb, all within the address block. It will be printed within the address block (or no-ink zone), indicated by a red box in your templates. 

Placement for 4x6" postcards only
Placement for all other postcards & self-mailers
Address block size (H x W): 2.375" x 3.2835"
  • Distance from right edge of return address: 0.32"
  • Distance from left edge of postage indicia: 0.25"
  • Distance from top edge of IMb code: 0.36"
Address block size (H x W): 2.375" x 4.0"
  • Distance from right edge of return address: 0.88"
  • Distance from left edge of postage indicia: 0.25"
  • Distance from top edge of IMb code: 0.46"

Placement on letters

On letters, the certification will appear to the right of the recipient address. The red area represents a white box, which will be printed on top of any submitted artwork to hold return and recipient addresses as well as the IMb information. This red box measures 2" x 3.15” (H x W), placed 0.6” from the left edge and 0.84” from the top edge of the trim.

The certification is not included on Certified letters or letters used in custom envelopes (#10 single-windowed).

Placement for letters ≤ 6 sheets 
(#10 Double-windowed envelopes)
Placement for letters > 6 sheets 
(Flat single-windowed envelopes)

Logo placement within red box:
  • From left edge of box: 2.53”
  • From right edge of box: 0.27”
  • From top edge of IMb code: 0.35”

Logo placement from letter edge (trim):
  • From left edge: 3.13”
  • From top edge: 1.84”
Logo placement within red box:
  • From left edge of box: 2.53”
  • From right edge of box: 0.27”
  • From top edge of IMb code: 0.35”

Logo placement from letter edge (trim):
  • From left edge: 3.13”
  • From top edge: 1.84”

For any questions on our eco-conscious certification, reach out to your CSM or support@lob.com.

QR codes & sequence ID numbers

On letters and checks, there is a small QR code and a set of sequence IDs that will be printed on the bottom left corner during the mail production process, which are used as part of Lob's internal quality control process. These codes get scanned by cameras on our printers to ensure that the correct pages go into each corresponding mail piece as they get inserted into envelopes. They will both appear on each page that contains content, and cannot be removed.

While the red zone around the QR code is 0.5" x 0.5" large, keep a 0.58" x 0.58" sized area at the bottom left corner of the letter clear of any content as it will be covered and obscured by a white box that will be printed around the QR code.   

Sequence IDs itself are 1.45" x 0.09" long, and is located 0.3" from the left edge and 2.2375" from the bottom edge of the page. Any content behind the sequence ID will be covered and obscured by a white box that will be printed to make the ID legible.

Plan your artwork submissions accordingly by avoiding printing any important text or artwork in the area saved for QR code and sequence numbers.

Intelligent Mail barcode

The Intelligent Mail barcode (IMb) is a 65-bar US Postal Service barcode used for mail sorting and tracking. It includes the routing ZIP and tracking information. USPS requires the use of the IMb in order for Lob's mail to benefit from automated processes.

Prohibited artwork

Stamp or indicia artwork: There is a risk that the USPS will reject mail that includes artwork that resembles a stamp or fake indicia. 

  • Postcards & self-mailers: Indicias are automatically printed within the address block (see above section). Fake indicias should not be part of your submitted artwork elsewhere.
  • Custom envelopes: There is no need to include indicia outlines in your artwork for the risk of rejection.

Artwork near the indicia: Artwork (such as eagles or American flags) is sometimes added to the left of an indicia box to add a sense of importance or urgency to a mailed piece. A 0.125" clearance on all sides from the indicia is necessary for this addition.  

Example: Fake indicia on postcard
Example: Artwork too close to indicia
Lob will print the actual indicia in the address block area
Leave enough space near indicia. No need to show the indicia box in artwork submissions, as Lob will print the indicia at the time of printing.

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