While there are many online resources offering information about people for a small cost, private investigators typically only utilize a few at a time and their use depends on the type of information they seek. For example, there are times when investigators only need to discover or monitor a subject’s social media activities. Other times, a person’s criminal history is most important. The problem is, some online tools yield a good amount of reliable and accurate information but most reveal unreliable and outdated data. One way of quickly knowing whether the investigative tool is legit or not is by seeing if the website delivers a vast collection of public information and, more importantly, reveals key content about the subject, such as the subject’s age and date of birth. These websites containing the most up to date and pertinent information are very rarely free. It is the paid investigative resources that are more reliably packed with extensive data that is more precise and organized.

Before diving into online tools and resources, remember that your town or county already has public records that you can access for free. But if you cannot find what you are looking for in those records, here are the most popular online tools for obtaining information on persons as well as businesses:

National Student Clearinghouse

Cost: $795 - $1,995 per year 
National Student Clearinghouse is an online database that tracks and verifies students major degrees and dates of attendance which is very efficient and helpful for schools with a vast number of students.

Investment Adviser Search

Cost: Free 
Investment Adviser Search allows you to search the complete compilation of Investment Adviser Firms currently registered with SEC and state securities regulators. Furthermore, the site has also a database of individual investment adviser representatives.

U.S Securities and Exchange Commission

Cost: Free 
Using Electronic Data Gathering, Analysis, and Retrieval (EDGAR), the U.S Securities and Exchange Commission allows you to pull up the electronic documents of companies registered under the SEC.

Bureau of Industry and Security - U.S Department of Commerce

Cost: Free
The Bureau of Industry and Security - U.S Department of Commerce allows you to view the Denied Persons List. A “Denied Person” is an individual whose export privileges have been forfeited by the Department of Commerce's Bureau of Industry and Security, also known as the BIS. A US company or individual is unable to participate in an export transaction with any persons or corporations on the Denied Persons List.

Open Secrets

Cost: Free/ Donation/ Custom Data Fee
Open Secrets is run by donations and can arrange custom data requests according to the federal campaign finance data you need. They can pull up data all the way back to 1979.

Council of International Investigators

Cost: Membership Fee
If you want to hire a private investigator worldwide, the Council of International Investigators is the right way to go. They have specialists available for every kind of investigation and have a vetting process to ensure quality.

Internet Archive

Cost: Free
A non-profit digital library containing millions of books, jobs, and people, Internet Archive consists of 330 billion web pages, 20 million books, and more.

Whois Domain Tool

Cost: Free
If you’re looking for an online entity, Whois Domain Tool enables you to trace the ownership and tenure of a domain name. Get hosting history, a name server report, reverse name, and domain search.

Federal Inmate Locator

Cost: Free
Federal Inmate Locator allows you to determine the whereabouts of U.S Bureau of Prisons inmates incarcerated from 1982 to the present.

Guidestar

Cost: Free
Comb through up-to-date records for 1.8 million IRS-recognized tax-exempt organizations from Guidestar, the world's largest source of information on nonprofit organizations.

Ancestry.com

Cost: 14-day Free trial
A well-known genealogy site, Ancestry.com does a lot more than uncovering ancient relatives. Using the site, you can discover in-depth family history, information about your ethnicity, retain access to global military records, and more.

Newspaper.com

Cost: 7-day Free trial
Newspaper.com boasts the largest online newspaper archive. You can use it to search historical newspapers from the 1700s to 2000s.

Indeed

Cost: Free
Indeed is a massive online resume database where you can find job listings and information about employers and applicants.

SpyDialer

Cost: Free
Search people via their phone number, name, address, and/or e-mail address by using SpyDialer which contains billions of phone numbers obtained using social media and user-contributed address books.

Historical Military Records

Cost: Free
The official repository for records of the U.S. Air Force, Army, Marine Corps, Navy and Coast Guard, and other government agencies. Historical Military Records provides access to records of veterans who separated from service after 1955.

World Organization of Detectives

Cost: Membership
The World Organization of Detectives is the foremost international association of professional investigators and security service organizations. Hire private investigator and security professionals worldwide.

Governmentattic

Cost: Free
Governmentattic provides access to the electronic copies of thousands of Federal Government documents obtained under the Freedom of Information Act.

The Work Number

Cost: $5-$50
Using the The Work Number, you can verify an employee’s employment, income, work number, social service, and more.