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Lob.com Letters API

The letters endpoint allows you to easily print and mail letters. The API provides endpoints forcreating letters, retrieving individual letters, canceling letters, and retrieving a list of letters.back to top

Lob.com Letters API is one of 32 APIs that Lob.com publishes on the APIs.io network, described by a machine-readable OpenAPI specification.

Tagged areas include Letters. The published artifact set on APIs.io includes an OpenAPI specification.

This API exposes 4 operations across 2 paths, and defines 82 schemas. It is described by OpenAPI 3.2.0, at version 1.22.0.

Requests are made against a single base URL, https://api.lob.com/v1.

4 operations 2 paths 82 schemas 1 DELETE2 GET1 POST

Metadata

The identity and technical contract details declared by the specification.

Specification
OpenAPI 3.2.0
API Version
1.22.0
Base URL
https://api.lob.com/v1
Authentication
HTTP Basic
License
Terms of Service
Resource Areas
1

Authentication & Security 1

Lob.com Letters API declares 1 security scheme for authenticating requests. It accepts HTTP basic authentication (basicAuth). By default, every request must be authenticated.

Paths & Operations 4

Across 2 paths, the API surfaces 4 operations — 1 DELETE, 2 GET, 1 POST. Each is listed below with its method, path, parameters, and response codes.

Letters 4

The letters endpoint allows you to easily print and mail letters. The API provides endpoints for creating letters, retrieving individual letters, canceling letters, and retrieving…

GET
/letters/{ltr_id}
Retrieve
letter_retrieve 1 param → 200default
DELETE
/letters/{ltr_id}
Cancel
letter_cancel 1 param → 200default
GET
/letters
List
letters_list 12 params → 200default
POST
/letters
Create
letter_create 3 params body → 200default

Schemas 82

The contract defines 82 schemas that model the data the API accepts and returns. The most detailed are qr_code (10 properties), failure_reason_error (7 properties), generated (7 properties), editable (6 properties). Each schema is shown below with its type and property counts.

tmpl_id
string
Unique identifier prefixed with tmpl. ID of a saved [HTML template](section/HTML-Templates).
error
object
Lob uses RESTful HTTP response codes to indicate success or failure of an API request. In general, 2xx indicates success, 4xx indicate an input error, and 5xx…
1 property 1 required
company
stringnull
Either name or company is required, you may also add both. Must be no longer than 40 characters. If both name and company are provided, they will be printed on…
failure_reason
object
An object describing the reason for failure if the resource failed to render.
3 properties
date_filter
object
Filter by ISO-8601 date or datetime, e.g. { "gt": "2012-01-01", "lt": "2012-01-31T12:34:56Z" } where gt is , lt is <, gte is ≥, and lte is ≤.
failure_status_code
integer
A conventional HTTP status code: 401 - Authorization error with your API key or account 403 - Forbidden error with your API key or account 404 - The requested…
adr_id
string
Unique identifier prefixed with adr.
date_created
string
A timestamp in ISO 8601 format of the date the resource was created.
address_editable_intl
bo_id
string
Unique identifier prefixed with bo.
editable
object
6 properties
print_speed
stringnull
A string designating the mail speed type: core - 2 production business days
inline_address_intl
evnt_id
string
Unique identifier prefixed with evnt.
address_fields_us
object
5 properties 4 required
certified
mail_type
string
A string designating the mail postage type: uspsfirstclass - (default) uspsstandard - a cheaper option which is less predictable and takes longer to deliver. u…
address_fields_intl
object
5 properties 2 required
vrsn_id
string
Unique identifier prefixed with vrsn.
deleted
boolean
Only returned if the resource has been successfully deleted.
ltr_id
string
Unique identifier prefixed with ltr.
thumbnail
object
3 properties
signed_link
string
A [signed link](section/Asset-URLs) served over HTTPS. The link returned will expire in 30 days to prevent mis-sharing. Each time a GET request is initiated, a…
input_from
object
1 property
buckslip_description
stringnull
Description of the buckslip.
ltr_size
string
Specifies the size of the letter. It accepts two values usletter and uslegal. If the [Lob-Version header](tag/Versioning-and-Changelog) in the request is set t…
inline_address_us
date_modified
string
A timestamp in ISO 8601 format of the date the resource was last modified.
ltr_file
Notes: - HTML merge variables should not include delimiting whitespace. - All pages of a supplied PDF file must be sized at 8.5"x11", while supplied HTML will…
failure_reason_error
object
Failure error details
7 properties
country_extended
string
Must be a 2 letter country short-name code (ISO 3166). Does not accept US, AS, PR, FM, GU, MH, MP, PW, or VI. For these addresses, please use the US verificati…
from
object
1 property
remote_file_url
string
The location of a remote file. Remote URLs have a 5 MB file size limit and must be downloaded within 40 seconds.
input_to
object
1 property
returned-2
objectnull
A nested custom envelope object containing more information about the custom envelope used or null if a custom envelope was not used.
3 properties 3 required
expected_delivery_date
string
A date in YYYY-MM-DD format of the mailpiece's expected delivery date based on its senddate.
card_id
string
Unique identifier prefixed with card.
extra_service
stringnull
Add an extra service to your letter. Can only be non-null if mailtype isn't uspsstandard. See pricing for extra costs incurred. certified - track and confirm d…
billing_group_id
string
An optional string with the billing group ID to tag your usage with. Is used for billing purposes. Requires special activation to use. See Billing Group API fo…
tracking_event_normal
count
integer
number of resources in a set
color
boolean
Set this key to true if you would like to print in color. Set to false if you would like to print in black and white.
buckslip_base
object
2 properties
html_string
string
An HTML string of under 10,000 characters.
return_address
Specifies the address the return envelope will be sent back to. This is an optional argument that is available if an account is signed up for the return envelo…
buckslip_id
string
Unique identifier prefixed with bck.
address_placement
string
Specifies the location of the address information that will show through the double-window envelope. To see how this will impact your letter design, view our l…
resource_description
stringnull
An internal description that identifies this resource. Must be no longer than 255 characters.
card
address_editable_us
letter_editable
address_intl
address_us
buckslip
registered
tracking_event_certified
merge_variables
objectnull
You can input a merge variable payload object to your template or QR code redirect URLs to render dynamic content. For example, if you have a template like: {{…
ltr_use_type
stringnull
The use type for each mailpiece. Can be one of marketing, operational, or null. Null usetype is only allowed if an account default usetype is selected in Accou…
user_provided-2
Indicates if a return envelope is requested for the letter. The value corresponding to this field is by default a boolean. But if the account is signed up for…
double_sided
boolean
Set this attribute to true for double sided printing, or false for for single sided printing. Defaults to true.
no_extra_service
inline_address
send_date
string
A timestamp in ISO 8601 format which specifies a date after the current time and up to 180 days in the future to send the letter off for production. Setting a…
lob_base
object
4 properties 3 required
metadata
object
Use metadata to store custom information for tagging and labeling back to your internal systems. Must be an object with up to 20 key-value pairs. Keys must be…
buckslip_order
letter
status
string
A string describing the PDF render status: processed - the rendering process is currently in progress. rendered - a PDF has been successfully rendered of the m…
generated
object
7 properties 2 required
list
object
Multiple items returned in order
5 properties
campaign_id
stringnull
Denotes resources created by the provided campaign id, prefixed with cmp. In the case of snap packs, booklets, and letters with size uslegal, however, the camp…
tracking_event_details
object
4 properties 3 required
user_provided
stringnull
Accepts an envelope ID for any customized envelope with available inventory. If no inventory is available for the specified ID, the letter will not be sent, an…
returned-5
object
4 properties
address
letter_generated_base
tracking_event_base
object
As mail pieces travel through the mail stream, USPS scans their unique barcodes, and Lob processes these mail scans to generate tracking events.
5 properties 4 required
letter_deletion
object
Lob uses RESTful HTTP response codes to indicate success or failure of an API request. In general, 2xx indicates success, 4xx indicate an input error, and 5xx…
2 properties
card_description
stringnull
Description of the card.
object
string
Value is resource type.
card_base
object
2 properties
qr_code
object
Customize and place a QR code on the creative at the required position.
10 properties 3 required

Specification

The full machine-readable OpenAPI contract behind this narrative.

Source

lobcom-letters-api-openapi.yml Raw ↑

Other APIs Lob.com publishes across the network.

Lob.com Accounts API
Lob.com Addresses API
Lob.com Bank Accounts API
Lob.com Billing Groups API
Lob.com Booklets API
Lob.com Buckslip Orders API
Lob.com Buckslips API
Lob.com Campaigns API
Lob.com Card Orders API
Lob.com Cards API
Lob.com Checks API
Lob.com Creatives API
Where this information came from

This is an independent, third-party profile of Lob.com Letters API, published by API Evangelist. We do not operate, host, resell, or support these APIs, and we are not affiliated with or endorsed by the company unless stated above. Everything here is built from publicly available information — the company's own site, developer portal, documentation, public repositories, and the specifications it publishes for public use. Nothing is obtained by breaching a system, defeating an access control, or using credentials.

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