Plagiarism is an essential Internet problem hurting both your feelings and your site rankings. While both Google and webmasters are figuring out how to combat it, let’s have a look at web-based plagiarism checkers to help you find the thieves:
| Data source | Registration | Reliability | Usability | |
| Copyscape.com | Google’s Web APIs | No (for free version) | 90% | high |
| Doc Cop | Google, Yahoo, Live | required | 80% | moderate |
| Plagiarism Detect | required | 50% | low | |
| Reprint Writers’ tool | Yahoo | no | 60% | moderate |
| Copyright Spot | Yahoo? | no | 45% | moderate |
(Note: Reliability and Usability columns reflect my personal opinion; please share yours!)
1. Copyscape.com has both a free (no registration required) and paid versions. The free one will search by the page URL and show only top 10 results. You can then go to each result and see the duplicated content highlighted.
The Premium account holders can submit text and see if it is plagiarized anywhere:
2. Doc Cop requires registration (with email confirmation). Its free version allows for only 75-word text check and no more than two checks a day.
The service essentially grabs short extracts from the submitted text and checks for exact match in Google, Yahoo and Live. Having found the duplications, it generates a report and sends it to your email.
(You will then have to go to each search engine result page to see which pages mention each string.)
3. Plagiarism Detect (registration required) also checks the submitted text; besides you can upload a txt or doc files. It will randomly choose strings of the text and search Google for the exact match.
After that, it will generate a quick domain-report as well as list the found results highlighting the string searched.
The strings the tool sometimes choose seem too short and thus results returned are not necessarily cases of plagiarism.
4. Reprint Writers’ tool requires no registration and the process is similar to the above: it grabs a few (long enough) word strings and checks Yahoo for the exact matches.
5. Copyright Spot checks the URL you submit and claims to find all your blog content thieves. It seems to grab most prominent phrases of the page (titles and headings) and check for the exact matches.
It is both free and open for use without registration, yet lacks reliability (it obviously returns better results if you check for subpages instead of the whole site).
The tool is new and promising, so we will be looking for essential improvements in the future.
Please also do check this list by BlogHerald listing more tools to help you prevent, find and report plagiarism.