Self-plagiarism is the same as regular plagiarism, however, the person whose content you are plagiarizing is you! Plagiarism is seen as theft, where you steal others’ intellectual/ creative/ academic property without giving them due credit. Self-plagiarism happens when you recycle or reuse parts of text from a paper you had submitted or published already. 
While the question of using someone else’s original idea and claiming it as your own is what defines regular plagiarism, in self-plagiarism the lines are somewhat blurry. This is because here, the original idea was also your own and you are not claiming anyone else’s work without credit.. You are, however, borrowing without giving the original author, i.e. yourself, due credit.

What does self-plagiarism include? 

Self-plagiarism (also called auto-plagiarism) can be committed in many ways, including:

Submitting a manuscript for publication in a journal, which contains data and verbatim text passages taken from a work that has already been published, without citing your previous work

Submitting an assignment written by you for a different academic year for a class in your present one

Reusing parts of an old assignment verbatim without proper citations (e.g., copy-pasting paragraphs from previously submitted work)

Using a dataset from another study

Submitting a manuscript for publication that contains pre-published data without citation of your previous publication

Publishing multiple similar papers about the same study in different journals

Self-plagiarism: Unethical or illegal?

Since you are not stealing or copying from someone else, it may seem like self-plagiarizing is not a serious offense. While it is not exactly illegal to self-plagiarize, it is certainly unethical. That is because, even though it is your original idea, you are passing off an old idea as new. Also, if someone is conducting institutionalized academic research, self-plagiarism can be a serious issue, because your institution provides funds and other resources like laboratory or library access for "original research," and not recycling old ones. Also, it is a misrepresentation of the time when you conceived the idea. Additionally, it can result in a copyright breach if the same content is published as an original research article by different journals.
Therefore, one might say that unlike other categories of plagiarism, self-plagiarism is not illegal. However, it is unethical to republish content without appropriate citations, irrespective of the fact that you are the original ideator. 

How can you avoid self-plagiarism?

Understand what plagiarism is

The first step to avoiding plagiarism is to understand what constitutes plagiarism. For example, you may not even be mindful of the fact that paraphrasing an idea without giving due credit is a form of plagiarism. Even incorrectly or insufficiently appropriating a work (whether someone else’s or your own) is considered plagiarism. The best way to avoid plagiarism is to be clear on what exactly plagiarism constitutes so that you will be able to organically check yourself if you are straying toward plagiarism while writing your manuscript or any other kind of textual content which requires original ideation

Organization and planning

Plan your paper and the topic you will be writing on, well in advance. Procrastination can sometimes lead you to be dangerously close to a submission deadline, at which point recycling a previously written paper feels like an easy way out. Even if you are writing different papers, if the topics are quite similar, it can lead to self-plagiarism. Therefore, you should carefully plan your writing and research schedules, to avoid writing on the same topic. Also, it is always a good practice to keep detailed notes and to keep revisiting your previously written and published/ submitted papers to ensure there is no accidental plagiarism happening.

Refer to your previously published/ submitted articles

There are multiple ways in which this can be done, for example:

Re-using your text can be acceptable in some cases, as long as there is some transparency and you let your reader know that the text you are using has been previously published/ submitted. You can do this by adding a formal statement in the manuscript declaring that some parts of the text are taken from another one of your works.

You can use the technique of putting quotation marks around text that you might have taken from your other work. You also need to state that you are the author of the said quote and also mention the date of its first appearance.

You may use a lead-in when introducing an idea you have used previously that identifies your original work when summarizing or paraphrasing. This is a great way of making your audience aware of which parts of your manuscript are borrowed from your previous work. Often, your lead-in is merely a dependent clause before your main statement. However, you can also include a sentence-long lead-in, if needed.
For example: In my paper titled, “…” I reviewed the difference between apples and oranges in the following manner:

The best way to avoid self-plagiarism is to treat it like you would treat references from any other source in your paper, i.e., with proper citation formatted according to the pertinent writing style. Whether you quote from or paraphrase/ summarize from a source that was previously written by you, ensure that it has been correctly cited. Cite your work in the appropriate format like APA, MLA, CMOS, etc. with your name, page numbers, date of publication, etc. just like you would do for any other citation.

If your paper has been published in a journal or a website, the publishers may hold copyrights to your article. You will need to ask their permission to reuse ideas from that piece. Otherwise, there could be an infringement of copyright.

Use a plagiarism detection tool like Enago’s plagiarism checker powered by Turnitin

There are quite a few ai plagiarism remover tools available online from basic ones to those powered with sophisticated AI-based technology. Enago’s Plagiarism and AI Grammar Checker is a globally top-ranked plagiarism checker that follows a double-pronged approach to help students, scholars, faculty, and other academic organizations eliminate plagiarism and grammar errors in one go.
We have partnered with the world’s leading plagiarism detection service provider Turnitin, whose expansive database and algorithms are used by 1700+ top publishers and peer reviewers (including Elsevier, Wiley, Sage, Taylor & Francis, and Springer).
Also, keeping in mind our student-friendly policy, our ai plagiarism remover services start from $12  only, while other tools can quote upward of hundreds of dollars. 
Enago’s Plagiarism and AI Grammar Checker can be used to process a wide variety of scholarly works, including student college assignments, student theses, technical reports, preprint articles, conference articles, and research papers. 
You can also upgrade your experience of using our Plagiarism and AI Grammar Checker service by opting for Advanced Checks, i.e., our “Scholarly Articles Check” option starting at $19, which compares your article against an additional 82+ million paid published scholarly articles. We also have the option for a “Power Editing” add-on coming soon, starting at an additional $6 over the basic package in which you can get up to 40% more suggestions for the same content. This service is developed using an exceptionally sophisticated AI engine that delivers 92% accuracy while maintaining—and in some cases, enhancing—the quality and integrity of your research writing.
Try Enago's ai plagiarism remover & Auto Grammar Check NOW!