PRESENTING A CONTENT ITEM TO AN ONLINE SYSTEM USER INCLUDING CONTENT DYNAMICALLY GENERATED BY THE ONLINE SYSTEM FOR THE USER

1 . A method comprising:

receiving, at an online system, product data describing characteristics of a product being offered by a third party system;

receiving, at the online system, a content item for presentation to one or more users of the online system, the content item being associated with a goal and one or more constraints and including a creative presenting content describing the product, the creative including one or more placeholder components

identifying, by the online system, an opportunity to present a content item to a user of the online system;

responsive to identifying the opportunity to present the content item,

accessing product engagement data for the user, the engagement data identifying previously accessed products of the user;

determining a likelihood of the user interacting with the content item for the product based on the accessed product engagement data for the user identifying the previously accessed products of the user; and

determining, for the third party system, a price of the product for the user based on the goal, the one or more constraints, and the determined likelihood of the user interacting with the content item for the product;

replacing, by the online system, a placeholder component of the creative for the content item with a price component for the determined price of the product for the user determined based at least in part on the determined likelihood of the user interacting with the content item for the product; and

providing, for display on a client device of the user, the content item including the creative presenting the content describing the product and an offer to purchase the product at the determined price.

2 . The method of claim 1 , further comprising:

receiving, from the client device of the user, an interaction with the content item corresponding to the user selecting the offer to purchase the product at the determined price; and

sending, by the online system, the user and offer data corresponding to the determined price for the product to a landing page for the product at the third party system, the landing page at the third party system displaying the offer to purchase the product at the price determined by the online system.

3 . The method of claim 1 , wherein the goal is a revenue goals corresponding to a total monetary value being received for the product from conversions via the content item.

4 . The method of claim 1 , wherein the determined price of the product for the user is different relative to at least one other user of the online system based on a different likelihood of the at least one other user interacting with the content item for the product.

5 . The method of claim 1 , wherein the product data further describes characteristics of a plurality of other products being offered by the third party system and the online system, responsive to identifying the opportunity to present the content item further,

identifies one or more candidate products of the plurality of other products including the product associated with the third party system for presentation to the user of the online system based on the accessed product engagement data for the user identifying the previously accessed products of the user and characteristics of the products associated with the third party system; and

selects the product of the candidate products based on likelihoods of the user accessing each of at least a set of the candidate products.

6 . The method of claim 5 , further comprising:

replacing, by the online system, an additional placeholder component of the one or more placeholder components of the creative for the content item with the product selected from the at least a set of the candidate products based on the likelihoods of the user accessing each of the at least a set of the candidate products.

7 . The method of claim 5 , wherein identifying the one or more candidate products of the products comprises:

retrieving characteristics of at least a set of the products offered by the third party system;

determining characteristics of products provided by the third party system accessed by the user of the online system from the received information; and

identifying candidate products as products from the at least the set of the products that have at least a threshold amount of characteristics matching characteristics of the products associated with the third party system accessed by the user.

8 . A method comprising:

obtaining, at an online system, product data describing characteristics of a product being offered by a third party system;

receiving, at the online system, a content item for presentation to one or more users of the online system, the content item including a creative presenting content describing the product;

receiving, from the third party system, a goal for the ad campaign and one or more constraints;

identifying an opportunity to present one or more content items to a user of the online system;

determining, for the third party system, a price of the product for the user based on the goal, the one or more constraints associated with the content item, and a likelihood of the user interacting with the content item for the product;

providing, for display on a client device of the user, the content item including the creative presenting the content describing the product and an offer for the product at the determined price;

receiving, from the client device of the user, an interaction with the content item corresponding to the user selecting the offer at the determined price; and

sending, by the online system, the user and offer data corresponding to the determined price for the product to a landing page for the product at the third party system.

9 . The method of claim 8 , wherein the price for the product is specific to the user and different relative to at least one other user of the online system.

10 . The method of claim 8 , wherein the price of the product is different for the user relative to the at least one other user of the online system based on a different likelihood of the at least one other user interacting with the content item for the product relative to the user.

11 . The method of claim 8 , wherein the landing page at the third party system displays the offer to purchase the product at the price determined by the online system.

12 . The method of claim 8 , wherein the goal corresponds to a total monetary value being received for the product from conversions via the content item.

13 . A non-transitory computer-readable storage medium having instructions that, when executed by a processor, cause the processor to:

receive, at an online system, product data describing characteristics of a product being offered by a third party system;

receive, at the online system, a content item for presentation to one or more users of the online system, the content item being associated with a goal and one or more constraints and including a creative presenting content describing the product, the creative including one or more placeholder components identify, by the online system, an opportunity to present a content item to a user of the online system;

access product engagement data for the user, the engagement data identifying previously accessed products of the user;

determine a likelihood of the user interacting with the content item for the product based on the accessed product engagement data for the user identifying the previously accessed products of the user;

determine, for the third party system, a price of the product for the user based on the goal, the one or more constraints, and the determined likelihood of the user interacting with the content item for the product;

replace, by the online system, a placeholder component of the creative for the content item with a price component for the determined price of the product for the user determined based at least in part on the determined likelihood of the user interacting with the content item for the product; and

provide, for display on a client device of the user, the content item including the creative presenting the content describing the product and an offer to purchase the product at the determined price.

14 . The non-transitory computer-readable storage medium of claim 13 , wherein the instructions, that when executed from the processor, further cause the processor to:

receive, from the client device of the user, an interaction with the content item corresponding to the user selecting the offer to purchase the product at the determined price; and

send, by the online system, the user and offer data corresponding to the determined price for the product to a landing page for the product at the third party system, the landing page at the third party system displaying the offer to purchase the product at the price determined by the online system.

15 . The non-transitory computer-readable storage medium of claim 13 , wherein the determined price of the product for the user is different relative to at least one other user of the online system based on a different likelihood of the at least one other user interacting with the content item for the product.

16 . The non-transitory computer-readable storage medium of claim 13 , wherein the product data further describes characteristics of a plurality of other products being offered by the third party system and the online system, responsive to identifying the opportunity to present the content item further,

identifies one or more candidate products of the plurality of other products including the product associated with the third party system for presentation to the user of the online system based on the accessed product engagement data for the user identifying the previously accessed products of the user and characteristics of the products associated with the third party system; and

selects the product of the candidate products based on likelihoods of the user accessing each of at least a set of the candidate products.

17 . The non-transitory computer-readable storage medium of claim 16 , wherein identifying the one or more candidate products of the products comprises:

retrieving characteristics of at least a set of the products offered by the third party system;

determining characteristics of products provided by the third party system accessed by the user of the online system from the received information; and

identifying candidate products as products from the at least the set of the products that have at least a threshold amount of characteristics matching characteristics of the products associated with the third party system accessed by the user.

18 . The non-transitory computer-readable storage medium of claim 16 , wherein the instructions, that when executed from the processor, further cause the processor to:

replace, by the online system, an additional placeholder component of the one or more placeholder components of the creative for the content item with the product selected from the at least a set of the candidate products based on the likelihoods of the user accessing each of the at least a set of the candidate products.

19 . The non-transitory computer-readable storage medium of claim 13 , wherein the goal is a revenue goals corresponding to a total monetary value being received for the product from conversions via the content item.

20 . The non-transitory computer-readable storage medium of claim 13 , wherein the determined price of the product for the user is different relative to at least one other user of the online system based on a different likelihood of the at least one other user interacting with the content item for the product.