Word fragments or n-grams have been widely used to perform different Natural Language Processing tasks such as information retrieval [1] [2], document categorization [3], automatic summarization [4] or, even, genetic classification of languages [5]. All these techniques share some common aspects such as: (1) documents are mapped to a vector space where n-grams are used as coordinates and their relative frequencies as vector weights, (2) many of them compute a context which plays a role similar to stop-word lists, and (3) cosine distance is commonly used for document-to-document and query-to-document comparisons. blindLight is a new approach related to these classical n-gram techniques although it introduces two major differences: (1) Relative frequencies are no more used as vector weights but replaced by n-gram significances, and (2) cosine distance is abandoned in favor of a new metric inspired by sequence alignment techniques although not so computationally expensive. This new approach can be simultaneously used to perform document categorization and clustering, information retrieval, and text summarization. In this paper we will describe the foundations of such a technique and its application to both a particular categorization problem (i.e., language identification) and information retrieval tasks.