The early years of Weber's eventful life are cloaked in obscurity, as relatively few documents survive to illuminate his life before 1810. He was the son of the Stadtmusicus and sometime Kapellmeister at Eutin, (2) Franz Anton Weber (1734–1812), and his second wife, the former Genovefa Brenner (1764–98). For most of his life Weber celebrated 18 December as his birthday, but he learnt in 1817 that the registry in Eutin recorded the date of his baptism as 20 November. In his later years he observed his birthday on 19 November, a date that coincided with his wife's presumed birthday and with the anniversary of their betrothal.
Weber's early biography is dominated by the activities of his father, a quixotic person who had appropriated the title ‘Baron’ and the ‘von’ in his name from an extinct Austrian noble family. Franz Anton resigned his position as Stadtmusicus in 1787 in order to form his own theatre company, composed largely of members of his own family. Between 1787 and 1794 the family travelled to Hamburg, Vienna, Kassel, Meiningen, Nuremberg, Bayreuth, Erlangen and Augsburg. In summer 1794 Genovefa, a soprano, was briefly engaged for Goethe's theatre in Weimar. The family troupe was in Salzburg in 1795 and 1796, now under the direction of Weber's half-brother Edmund. According to Carl Costenoble, a member of the company in 1795, its repertory included plays by Iffland and Kotzebue, and operas by Mozart, Wenzel Müller, Neefe and Edmund Weber. Costenoble also provides a picture of the boy Weber as a weak, lame child, and later sources confirm that he was afflicted by a congenital hip disorder that caused him to limp.
Because of Genovefa's pregnancy and fragile health, Franz Anton withdrew from the company and settled in Hildburghausen in 1796. About this time he evidently began to entertain the thought of developing his son into a child prodigy along the lines of Mozart. Weber, who had studied music with his father and older half-brothers, now took piano and thoroughbass lessons from the local organist, oboist and composer Johann Peter Heuschkel. Studies in counterpoint with Michael Haydn followed, when the family moved back to Salzburg in late 1797. (Genovefa died there on 13 March 1798.) From the lessons with Haydn emerged Weber's first known composition, a set of six four-voice fughettas published in open score (j1–6).
From late 1798 to August 1800 Franz Anton and Carl Maria made Munich their base, and the father continued his efforts to promote his son as a second Mozart. Weber studied singing with Giovanni Valesi and piano and composition with Johann Nepomuk Kalcher. According to his Autobiographische Skizze (1818), Weber composed while studying with Kalcher an opera (Die Macht der Liebe und des Weins), a mass, piano sonatas, several sets of variations, string trios and songs. He offered a number of these pieces to publishers in late 1800, but the only ones known to survive are the mass (in a manuscript copied in Salzburg in 1802) and a set of published variations (op.2). Following the Autobiographische Skizze and an early obituary (BAMZ 1826), Weber's principal biographer, his son Max Maria von Weber, claimed that the rest of these juvenilia was accidentally destroyed by a fire at Kalcher's, but the fact that Weber and his father were still offering these pieces to publishers in November 1801, by which time they had moved again to Salzburg, contradicts this. Instead, it is more likely that Weber himself destroyed the bulk of his juvenilia (as asserted in Gustav Schilling's Encyclopädie, 1835–8) some time in the first half of 1802.
In Munich father and son were introduced to lithography, a process used to print Weber's op.2, which was lithographed by Alois Senefelder's brother Theobald (not by Weber himself, as is often claimed in the literature). With plans to start their own lithographic business, the Webers moved to Freiberg in Saxony in September 1800. There Weber rapidly composed an opera, Das Waldmädchen, to a libretto by the local theatre director Carl von Steinsberg. Its première on 24 November 1800 in Freiberg and subsequent revival in Chemnitz in December triggered a heated exchange in early 1801, in the Freyberger gemeinnützigen Nachrichten für das chursächsische Erzgebirge, between Weber (doubtless guided by his father) and local musicians. In the wake of the controversy the Webers resettled in Chemnitz in March 1801. Apart from this opera, of which only parts of two pieces survive, Weber composed very little between autumn 1800 and the end of 1801 – 12 Allemandes for piano later published as op.4 are the only other original compositions known from this period – as he seems to have been distracted by his father's ultimately unsuccessful efforts at lithography.
After a brief stay in Munich in summer 1801, Weber and his father were again in Salzburg from November 1801 until July 1802. Beyond the possible revision of the early mass, the compositions of this period include a few canons and a new opera, Peter Schmoll und seine Nachbarn. Of importance for Weber's future development was his friendship in Salzburg with Thaddäus Susan (1779–1838), an amateur flautist and law student with whom he began to plan various literary and critical projects.
By August 1802 the Webers had left Salzburg for an extended tour to northern Germany. The tour is largely documented by an album that Weber kept from 1799 to 1812 (D-Bsb). Passing through Munich, where they had the libretto of Peter Schmoll printed, the Webers visited Augsburg, where they made the acquaintance of the publisher Gombart and it is likely that they sold Peter Schmoll to the local theatre. In Sondershausen Weber met Gerber, probably giving him autobiographical material for the revision of his music-biographical dictionary and also volunteering to write entries on Salzburg musicians for it. The tour continued to Hamburg, where Weber gave a public concert (30 October 1802) and composed his earliest surviving songs. According to his autobiographical sketch, he began to collect treatises on music theory on this trip in an attempt to answer technical and aesthetic questions that his earlier training had neglected. This claim is largely substantiated by the discovery in 1983, among the autographs of his letters to Gottfried Weber (US-NYpm), of a list of approximately 45 theoretical works, ranging from the 16th century to the most recent, that Weber had acquired before 1810 (Veit, G1988). Weber and his father returned to Augsburg in late 1802 in order to supervise the première of Peter Schmoll in spring 1803. Nothing is known of this production, and the opera achieved no further performances during Weber's lifetime.
An important watershed for Weber's early development was his stay in Vienna from August 1803 to May 1804, a sojourn that is principally documented by his letters to Susan, with whom he continued to discuss a number of ambitious literary projects. For the first time in his life, Weber was separated for an extended period from his father, who returned to Augsburg. More important, in Vienna Weber came under the tutelage of the theorist, organist and composer Georg Joseph Vogler, who was then at work on Samori, a new opera commissioned by the Theater an der Wien. Consisting largely in the analysis of Vogler's own works, the lessons with Vogler imparted to Weber that which he felt he needed most, a method for understanding the aesthetic reasons for compositional procedures. Through Vogler Weber gained entrée to the upper echelons of Viennese musical society, making the acquaintance of Salieri, Teyber, Gyrowetz, Schuppanzigh, Wranitzky, Hummel and even Joseph Haydn; interestingly, Weber's letters to Susan make no mention of Beethoven, whom Vogler may have regarded as a rival. However, the lessons with Vogler came at a price, as Vogler restrained Weber from composition for nine months and required him to prepare the vocal score for Samori. Further, when Vogler finally allowed Weber to compose again he instructed him to write two variation sets for piano based on his own theatrical works (j40, j43).