There are a number of free and paid software available for checking plagiarism. Free software you can find by just searching on google like Grammarly.
The paid software are not accessible until subscription fee is not paid by us.
The free software are having a major limitation that they cant clear the picture of plagiarism in the checked text.
The exact results are accessible with paid software such as Urkund, Turnitin, and iThenticate etc.
The best software in my opinion is Turnitin which is a paid software (if you can buy) or you can request someone from your friend circle who is having access to this wonderful software.
I use a combination of Grammarly (paid) and the similarity checker in Word’s editor. The free Grammarly plagiarism check only tells you that you have duplicate content in your text, but the paid version will tell you which passages are problematic. However, these should be used as a check and not as a replacement for staying organized to prevent plagiarism.
In my opinion, most of the free-software-checkers for plagiarism don't work effectively. Since there is no guarantee that the original content of your manuscript might not be copied and sold to others before it is published by you, I discourage using any free-software-checkers for plagiarism; some of them are betrayers.
WARNING 1: There are a massive number of betrayers!
WARNING 2: Plagiarism is a sin! If it is, severe action may be taken and/or legal notice may be given.
Unfortunately, you have to pay for the sake of getting good results. In any way, it is not well for your reputation if there were accusations of plagiarism.
In my personal opinion, free anti-plagiarism software is not safe.
On the other side, My university, WISE, uses the TURNITIN plagiarism checker. The maximum allowed percentage of plagiarism should be commonly less than 20%. However, from the same reference, it should not exceed 5%.
We must completely understand that the plagiarism is never allowed and it is almost impossible to have 0% similarity.
Plagiarism is a common problem facing almost all professors. This respected portal (i.e. RG) defines plagiarism as:
The term “plagiarism” has different meanings, but it usually includes copying somebody else’s work without permission.
On the other side, self-plagiarism is when the author republishes portions of his/her own previously written research work while authoring a new work.
I may be somewhat old-fashioned, but please have a look at the following golden principles on how to avoid plagiarism in academic writing, especially Self-Plagiarism:
Never use the "Copy-Paste" trend: Use your own words instead of copying and pasting the text verbatim from others (i.e. reference papers). On the other hand, I don't trust using the rewrite-websites to rephrase the text of other research articles. I only trust my own rephrasing. Needless to say that if you are using your own words, then there is no chance of plagiarism accusing. Try to paraphrase your content as much as you could.
Never repeat yourself: There are many re-published articles that are slightly or even considerably modified, and still not changed!
If you have co-authors, just trust your words!
If you use your own words, there should be no plagiarism issue. In turn, there is no need for the tools of plagiarism checking. Since there is no guarantee that the original content of your manuscript might not be copied and sold to others before it is published by you, I discourage using any free-software checkers for plagiarism; some of them are betrayers. Despite that offline ones are rare and if you are insisting to use anti-plagiarism software, offline checker programs are safer than online ones. On the other side and in case you are again insisting to use anti-plagiarism check, the process should be carried out for the entire research work, literature reviews, for instance, are not an exception.
In some cases, you can paraphrase the sentences (اعادة صياغة الجملة) in the original document. But don't forget to cite the reference.
You must always insist on honesty. Furthermore, you have to always remember that there should be a new added value.
You must always insist on doing real research, not "Wikipedia" research.
Do not put any of your research work anywhere until it is published and tagged with your name. Please wait until the paper is accepted and then published in that journal. Then, upload that research item on any platform you wish.
In my opinion, most of the free-software-checkers for plagiarism don't work effectively. Unfortunately, you have to pay for the sake of getting good results.
Despite that offline ones are rare and if you are insisting to use anti-plagiarism software, offline checker programs are safer than online ones.
Try to develop your own style for the text writing.
You should be should beware of storing your document in any portal that is used as free software checker for any language.
Try to read as much scientific literature as possible, especially in your own research field area.
Don't forget to cite your Sources: Identify what is needed and what is not needed to be cited. If you refer to any material, including images and data, you should be clear and define the source. Because images are treated as data in the case of citation, you should refer to any taken image and cite it in the references whether it has been copied from the social media image or a research article. By the way, please do not forget that "A picture is worth a thousand words"!
A reminder for all respected researchers: In order to maintain research integrity, plagiarism (الاستلال) has to be given up. However, many people do not know whether they are committing plagiarism intentionally or unintentionally. How we can be more concerned about this issue?
Now, I think that the above-mentioned rules are helping in setting boundaries to avoid plagiarism in general, and self-plagiarism in special.
Finally, believe me, or not: If you make one plagiarizing, you may solve one problem and fall into many others where some of which may be described as a knockout. Again and again, please always remember that if there were accusations of plagiarism, it is not well for any researcher's reputation, in any meaning.
Let me point to another critical issue related to plagiarism software-detectors. My friend was accused of plagiarism. Why?
After about five months, his promotion process to associate professor was rejected because of plagiarism. When he checked the promotion report, he found that one of his papers was accused of plagiarism and with a 100% percentage. The reason is that his manuscript was checked by his co-author using one of these checkers. It took him several months time of following up to solve the problem and removing the manuscript from their database. After that long period, he re-apply the promotion order for the second time.
Therefore, plagiarism software may retain a copy of the manuscript in its database. To state the truth, this is depending upon the settings and type of account subscription.
So, you may face a similar situation when you submit your manuscript after plagiarism checking to a journal. It may be rejected instantly because it would show up 100% similarity index.
To solve the problem, it may take several months time of following up and removing the manuscript from their database.
If there were accusations of plagiarism, it is not well for your reputation, in any meaning.