With social platforms being used by an increasing number of users, the Internet became a perfect place for extremist ideas and opinions to be created and propagated. Detection of extremist content can be an asset for security agencies but it comes with technical challenges and requires semi-automatic approaches, as reading the sheer amount of data released online is an impossible task for analysts. This paper investigates the use of learning models to detect extremist contents in French corpora and focuses on right-wing extremist detection. Several learning models have been developed including unsupervised approaches and neural ones. The models were applied to a data set gleamed online. Experiments show that data representation and parameters of models may affect the overall performance and extremist content can be accurately detected when parameters and thresholds are tuned correctly. These results are novel as they contribute to the analysis of social data conveying extremist ideas in French.