Sawyer's Anglo-Saxon Charters

 https://esawyer.lib.cam.ac.uk/about/index.html
The ‘Electronic Sawyer’ presents in searchable and browsable form a revised, updated, and expanded version of Peter Sawyer's Anglo-Saxon Charters: an Annotated List and Bibliography, published by the Royal Historical Society in 1968.

https://esawyer.lib.cam.ac.uk/browse/kinga/A.html
an alphabetical index which provides the user with an easy way to browse through the charters of a particular king (e.g. Offa, Alfred, Edgar, or Harold)

https://en.wikipedia.org/wiki/Anglo-Saxon_charters
Charters have provided historians with fundamental source material for understanding Anglo-Saxon England, complementing the Anglo-Saxon Chronicle and other literary sources. They are catalogued in Peter Sawyer's Annotated List and are usually referred to in the specialist literature by their Sawyer number (e.g. S 407).

For Example Charter 1008
 King Edward the Confessor of England grants seven hides at Millbrook, Hampshire, to Bishop Ælfwine of Winchester, 1045: Cotton Ch VIII 9

https://esawyer.lib.cam.ac.uk/charter/1008.html#
Grant of King Edward the Confessor (r. 1042–1066) to Bishop Ælfwine of Winchester

The Anglo Saxon Charters contain a wealth of information that may not be available elsewhere. They show, by examination of the pecking order of the witnesses, who was attending court at the time of the signing and their respective positions.
We can see in this one, the respective positions of the earls in 1045, with Earl Godwin of Wessex leading, followed by Leofric of Mercia and  Siward of Northumbria, followed by Godwin’s sons Sweyn and Harold and their cousin Beorn Ulfson.
 
“+ Ego Godwine dux. + Ego Leofric dux. + Ego Siwerd dux. + Ego Swegen dux. + Ego Harold dux. + Ego Beorn dux”

The actual charter can be seen here at the British Library Collection

The British Library holds the world's largest collection of Anglo-Saxon charters. They are issued in the names of kings, bishops and laypeople, and include a considerable number of writs, wills, records of disputes and decrees of synods. The charters supply significant testimony to the evolution of English handwriting (the scripts deployed include uncial, pointed minuscule, square minuscule and English Caroline minuscule). They are composed primarily in Latin but with a considerable number in Old English (or with Old English bounds). Some of the documents are originals or were issued contemporaneously, while others are later copies or are deemed to be forgeries. Collectively, these charters provide us with substantial evidence for early English political, ecclesiastical, administrative and social history.
http://www.bl.uk/manuscripts/FullDisplay.aspx?ref=Cotton_Ch_VIII_9