Professor Peter Sawyer's Anglo-Saxon Charters: an Annotated List and Bibliography was published by the Royal Historical Society in 1968. It was the first comprehensive listing of all surviving charters from the Anglo-Saxon period, containing over 1850 separate entries. The original 1968 catalogue soon came to be known in academic parlance as 'Sawyer', and references to charters are now conventionally given in the form 'S 000', where '000' represents the number of the charter in Sawyer's catalogue.

The publication of 'Sawyer' transformed the study of the surviving corpus of charters as a major part of our evidence for knowledge and understanding of Anglo-Saxon England. In 1991 the British Academy-Royal Historical Society Joint Committee on Anglo-Saxon Charters, formed in the mid-1960s to organize the production of a new multi-volume edition of the charters, recognized that there was also a need for a revised edition of Sawyer's catalogue. The project was duly set in motion, and now takes the form of the electronic database, devised and maintained by a research team in Cambridge, known as the 'Revised Sawyer'.

The 'Revised Sawyer' aims, like its predecessor, to provide a systematic, accurate and complete coverage of all documents falling within its scope (royal diplomas, royal writs, 'private' [non-royal] charters, vernacular documents, etc.), genuine and forged, with references to all manuscripts in which a given text has been preserved, to all published editions and translations, and to places in books or articles where any aspect of a charter is discussed (e.g. palaeography, authenticity, place-names, boundary clauses, language, formulation (diplomatic), literary interest, historical interest, witnesses, later use).

The 'Electronic Sawyer' is an online manifestation of the 'Revised Sawyer', devised and maintained by a team at the Centre for Computing in the Humanities at King's College London. It made its first appearance online in 2007, in its 'beta' stage of development. It was launched, after further development, in the autumn of 2010; the process of its development will of course be taken further.

The overall structure of the catalogue, showing how the separate entries are arranged and classified, can be seen by clicking on Sawyer Catalogue in the 'Browse' menu.

The format of the separate entries in the 'Revised Sawyer', and so in the 'Electronic Sawyer', is developed from Professor Sawyer's original catalogue published in 1968. An entry for a standard royal diploma comprises the following elements:

  • S 000 The 'Sawyer' number which identifies a particular charter.
  • [Title:] The date, followed in brackets by any indication of the precise day on which and place where the charter was issued. Brief summary of the charter, naming the issuing authority (i.e. the king), the beneficiary, and the nature of the transaction. A royal diploma is almost invariably in Latin, though might have a boundary-clause in English.
  • Archive: Name of the religious house among the muniments of which the charter was preserved during the Middle Ages, in some cases in its original (single-sheet) form, but in most cases in the form of a copy entered in the 11th century or later in a cartulary (register of charters). Some of the manuscripts remain where they have always been, for example in the cathedral archives at Canterbury, or Exeter, or at Westminster Abbey; most are now in the British Library or in other major repositories; a few are in private hands.
  • MSS: List of the particular manuscripts in which a text of the charter occurs. In certain cases, the list begins with a 'single sheet', i.e. a text of the charter written on a single sheet of parchment in a hand contemporary with the given date, or perhaps in a later hand. In many cases, the list will include one or more cartularies or registers of the religious house. In some cases, the list will include copies made by central authorities when charters were submitted for inspection or confirmation, preserved in what used to be the Public Record Office (Chancery Lane), now moved to The National Archives (Kew). In some case the list might include transcripts made by antiquaries in the seventeenth or eighteenth centuries. A button placed beside a particular manuscript gives a facsimile of the manuscript in question (whether single sheet, cartulary copy, or early modern transcript). This feature is under development.
  • Printed: List of the printed editions of the charter, from its first published appearance (perhaps as early as the seventeenth century) to its most recent. 'K', followed by a number, indicates the 6-volume edition of charters published by John Mitchell Kemble in 1839–48; 'B', followed by a number, indicates the 3-volume of charters (up to 975) published by Walter de Gray Birch in 1885–93.
  • Comments: List of published references to the charter, with brief indication of their content, e.g. on formulation, on authenticity, on matters of identification, or on historical interest.

In many cases, entries are followed by a button labelled 'Text', and by another button labelled 'Old Text'. The former gives the text of a charter if contained in one of the published volumes of the new edition (published by the British Academy). The latter gives an older (perhaps less accurate) text, generally derived from 'Kemble' or 'Birch'. In some cases, a button labelled 'Translation' gives a translation of the text into modern English, if one is available.

In 2007 the bibliography in the Revised Sawyer database contained about 20 items published before 1700; about 40 items published in the 18th century; about 160 items published in the 19th century; about 475 items published in the period 1900–69; about 600 items published in the period 1970–99; and about 50 items published in 2000–7. Many of the 'new' items in the bibliography contain only one or two references to particular charters; but some others (including several published after c. 1970) contain a large number of references. References are still being gathered from other publications which have appeared since c. 2000, not yet included in the bibliography, and will be uploaded to the database on a regular basis.