Here are the differences:
An OPT is available to eligible F1 visa students who are allowed - if they meet the qualifications - to apply their specialized knowledge to a directly related job. After completing the first academic year, F-1 students are eligible to work in three different types of off-campus employment:
- Curricular Practical Training (CPT)
- Optional Practical Training (OPT) (pre- or post-completion)
- Science, Technology, Engineering and Mathematics (STEM) Optional Practical Training Extension (OPT)
Any off-campus employment after the first academic year must be directly related to the area of study and be authorized by the designated school official and US Citizenship and Immigration Services (USCIS) prior to starting any work.
An EAD is an Employment Authorization Document issued to foreign workers who fall into certain immigrant and nonimmigrant categories - for instance, for those who have filed a Form I-485 Application to Register for Permanent Residence or Adjust Status.
Since US employers are required to verify the eligibility of all employees who seek to work inside the US, the EAD is the document you submit to your employer proving that permission. Most EADs are valid for one year.
An H-1B is program is available to F1 students who want to gain practical work experience - inside the US - in a job that’s related to their field of study. F1 students can change their status from F1 to H-1B by securing a qualified H1B position with an H-1B sponsor company.
However, H-1Bs are also available to foreign nationals who are not students. US companies use the H-1B visa to hire foreign professionals for specialty occupations. This requires that the worker has at least a four-year degree or the equivalent in experience. When the H-1B is approved, the professional can work only for the position stated on the H-1B petition. If the person wishes to change employers, the new employer must file a new petition.