Quick & concise walkthrough on how you can create a Custom Audience on Facebook for FB ads. You can use this technique to build an audience from your competitor’s Facebook groups or multiple Facebook Groups wherever your target audience is.
We will be using the Facebook Group Member Extractor tool from Prospectss.com to get the required data from the Facebook Groups.
Step 1: Identify Facebook Groups to Scrape Data for Custom Audience
Find multiple groups that fall into your target audience/niche. Ideally, try for groups with more than 10k members. We would be able to create a custom audience from both public and private groups.

For private groups, we have to be a member of that group. This shouldn’t be a problem; join the group if you are not a member.
Step 2: Scrape Facebook Member Data
Once you have identified the group that you want to scrape, we will move forward and use Facebook Group Scraper from Prospectss.
You would need to Signup on Prospectss and Install the extension for scraping the data. You can initially signup for their Free plan.

Signup for Prospectss: https://prospectss.com/app/signup
Link to the Chrome Extension: https://chrome.google.com/webstore/
detail/email-extractor-for-fb-gr/fdooaeafkeckhgbnbmodmjkjpfmjcbnh
You would need to use the Account Key from Prospectss and use it inside the extension to authenticate. Account Key is visible from the navbar or you can also get it from your profile page.

Once you have successfully authenticated your extension with the account key, Visit the Members sections on the group page and open the extension to start scraping. If the start scraping button doesn’t appear, refresh the page.


Use the start scraping button to start the process, it should take a few minutes to scrape around 10k members. You can scrape as many members as you want. The more, the better. Sometimes you might face a rate limit issue from Facebook. Ideally, the rate limit is lifted in around 4 to 24 hours. Once the scrape is complete, it will appear on the Prospectss site here. You can download the all data with emails or download data with only emails, we would go with Download All Data with Emails. Unlock the data and download the CSV & head onto Facebook Ad Manager.
Step 3: Build Custom Audience with the Data
Open Facebook Ads Manager & visit the Audiences page.

On the audience page, Click on the Create Audience button and choose Custom Audience.

Quick Tip: Upload the scraped data of minimum 20k members to make the most out of the Ad. Scrape multiple groups & combine that data then upload it.
Then, Hit the Next button.
You will be then asked to select the List Type, & choose “No” unless you want to try some experimentation. Hit Next to proceed.
You will now be asked to upload the data list CSV. Don’t download the template that they have provided, instead directly upload the CSV that we have downloaded from Prospectss.com

Choose the correct name for your audience and Hit Next to proceed.
Open up your custom audience tab, and create a new audience using CSV data. Facebook requires a lot of parameters for uploading the data for the custom audiences, however, all of the parameters are not compulsory, although the more the merrier. We can choose the following data points from the CSV that we downloaded from prospectss and match it with custom audience parameters, check the image for more details. Once done, uploading this data and building the custom audience will take some time. Once done custom audience will start showing up for you, however, take note that it won’t show you the size of the audience as Facebook has stopped sharing the audience size with ad managers.
To sum it up, find relevant groups, use prospectss.com to scrape the data from the group, & use the data to build the audience.
Some pretty slick tricks to get more Return On Assets (ROAs) for your ads using this custom audience are to find all of your competitor groups and build the custom audience with that.
If you have any questions or ideas, do share them in the comments.