diff --git a/flag.go b/flag.go
index 2bd83ff..551e0cf 100644
--- a/flag.go
+++ b/flag.go
@@ -10,7 +10,7 @@ import (
 )
 
 func init() {
-	flag.StringVar(&util.URL, "url", "http://0.0.0.0:$port", "URL at which your wiki can be found. Used to generate feeds")
+	flag.StringVar(&util.URL, "url", "http://0.0.0.0:$port", "URL at which your wiki can be found. Used to generate feeds and social media previews")
 	flag.StringVar(&util.ServerPort, "port", "1737", "Port to serve the wiki at using HTTP")
 	flag.StringVar(&util.HomePage, "home", "home", "The home page name")
 	flag.StringVar(&util.SiteTitle, "title", "🍄", "How to call your wiki in the navititle")
diff --git a/http_readers.go b/http_readers.go
index 6f7c58e..497a30f 100644
--- a/http_readers.go
+++ b/http_readers.go
@@ -36,7 +36,7 @@ func handlerRevision(w http.ResponseWriter, rq *http.Request) {
 		textContents, err = history.FileAtRevision(textPath, revHash)
 	)
 	if err == nil {
-		contents = markup.ToHtml(hyphaName, textContents)
+		contents = markup.Doc(hyphaName, textContents).AsHTML()
 	}
 	treeHTML, _, _ := tree.Tree(hyphaName, IterateHyphaNamesWith)
 	page := templates.RevisionHTML(
@@ -81,20 +81,27 @@ func handlerPage(w http.ResponseWriter, rq *http.Request) {
 		hyphaName         = HyphaNameFromRq(rq, "page")
 		data, hyphaExists = HyphaStorage[hyphaName]
 		contents          string
+		openGraph         string
 	)
 	if hyphaExists {
 		fileContentsT, errT := ioutil.ReadFile(data.textPath)
 		_, errB := os.Stat(data.binaryPath)
 		if errT == nil {
-			contents = markup.ToHtml(hyphaName, string(fileContentsT))
+			md := markup.Doc(hyphaName, string(fileContentsT))
+			contents = md.AsHTML()
+			openGraph = md.OpenGraphHTML()
 		}
 		if !os.IsNotExist(errB) {
 			contents = binaryHtmlBlock(hyphaName, data) + contents
 		}
 	}
 	treeHTML, prevHypha, nextHypha := tree.Tree(hyphaName, IterateHyphaNamesWith)
-	util.HTTP200Page(w, base(hyphaName, templates.PageHTML(rq, hyphaName,
-		naviTitle(hyphaName),
-		contents,
-		treeHTML, prevHypha, nextHypha)))
+	util.HTTP200Page(w,
+		templates.BaseHTML(
+			hyphaName,
+			templates.PageHTML(rq, hyphaName,
+				naviTitle(hyphaName),
+				contents,
+				treeHTML, prevHypha, nextHypha),
+			openGraph))
 }
diff --git a/hypha.go b/hypha.go
index e412c14..5280639 100644
--- a/hypha.go
+++ b/hypha.go
@@ -33,6 +33,12 @@ func init() {
 		return
 	}
 	markup.HyphaIterate = IterateHyphaNamesWith
+	markup.HyphaImageForOG = func(hyphaName string) string {
+		if hd, isOld := GetHyphaData(hyphaName); isOld && hd.binaryPath != "" {
+			return util.URL + "/binary/" + hyphaName
+		}
+		return util.URL + "/favicon.ico"
+	}
 }
 
 // GetHyphaData finds a hypha addressed by `hyphaName` and returns its `hyphaData`. `hyphaData` is set to a zero value if this hypha does not exist. `isOld` is false if this hypha does not exist.
diff --git a/markup/img.go b/markup/img.go
index 9539498..99c919b 100644
--- a/markup/img.go
+++ b/markup/img.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"regexp"
 	"strings"
+
+	"github.com/bouncepaw/mycorrhiza/util"
 )
 
 var imgRe = regexp.MustCompile(`^img\s+{`)
@@ -184,6 +186,14 @@ func (img *Img) binaryPathFor(path string) string {
 	}
 }
 
+func (img *Img) ogBinaryPathFor(path string) string {
+	path = img.binaryPathFor(path)
+	if strings.HasPrefix(path, "/binary/") {
+		return util.URL + path
+	}
+	return path
+}
+
 func (img *Img) pagePathFor(path string) string {
 	path = strings.TrimSpace(path)
 	if strings.IndexRune(path, ':') != -1 || strings.IndexRune(path, '/') == 0 {
diff --git a/markup/lexer.go b/markup/lexer.go
index 6ba3b94..b1c3abc 100644
--- a/markup/lexer.go
+++ b/markup/lexer.go
@@ -9,6 +9,9 @@ import (
 // HyphaExists holds function that checks that a hypha is present.
 var HyphaExists func(string) bool
 
+//
+var HyphaImageForOG func(string) string
+
 // HyphaAccess holds function that accesses a hypha by its name.
 var HyphaAccess func(string) (rawText, binaryHtml string, err error)
 
@@ -29,21 +32,21 @@ type GemLexerState struct {
 
 type Line struct {
 	id int
-	// interface{} may be bad. What I need is a sum of string and Transclusion
+	// interface{} may be bad. TODO: a proper type
 	contents interface{}
 }
 
-func lex(name, content string) (ast []Line) {
-	var state = GemLexerState{name: name}
+func (md *MycoDoc) lex() (ast []Line) {
+	var state = GemLexerState{name: md.hyphaName}
 
-	for _, line := range append(strings.Split(content, "\n"), "") {
-		geminiLineToAST(line, &state, &ast)
+	for _, line := range append(strings.Split(md.contents, "\n"), "") {
+		lineToAST(line, &state, &ast)
 	}
 	return ast
 }
 
 // Lex `line` in markup and save it to `ast` using `state`.
-func geminiLineToAST(line string, state *GemLexerState, ast *[]Line) {
+func lineToAST(line string, state *GemLexerState, ast *[]Line) {
 	addLine := func(text interface{}) {
 		*ast = append(*ast, Line{id: state.id, contents: text})
 	}
diff --git a/markup/mycomarkup.go b/markup/mycomarkup.go
index f3fb7a2..656ca28 100644
--- a/markup/mycomarkup.go
+++ b/markup/mycomarkup.go
@@ -2,8 +2,12 @@
 package markup
 
 import (
+	"fmt"
 	"html"
+	"regexp"
 	"strings"
+
+	"github.com/bouncepaw/mycorrhiza/util"
 )
 
 // A Mycomarkup-formatted document
@@ -11,24 +15,75 @@ type MycoDoc struct {
 	// data
 	hyphaName string
 	contents  string
+	// indicators
+	parsedAlready bool
+	// results
+	ast           []Line
+	html          string
+	firstImageURL string
+	description   string
 }
 
 // Constructor
 func Doc(hyphaName, contents string) *MycoDoc {
-	return &MycoDoc{
+	md := &MycoDoc{
 		hyphaName: hyphaName,
 		contents:  contents,
 	}
+	return md
+}
+
+func (md *MycoDoc) Lex(recursionLevel int) *MycoDoc {
+	if !md.parsedAlready {
+		md.ast = md.lex()
+	}
+	md.parsedAlready = true
+	return md
 }
 
 // AsHtml returns an html representation of the document
 func (md *MycoDoc) AsHTML() string {
-	return ""
+	md.html = Parse(md.Lex(0).ast, 0, 0, 0)
+	return md.html
 }
 
+// Used to clear opengraph description from html tags. This method is usually bad because of dangers of malformed HTML, but I'm going to use it only for Mycorrhiza-generated HTML, so it's okay. The question mark is required; without it the whole string is eaten away.
+var htmlTagRe = regexp.MustCompile(`<.*?>`)
+
 // OpenGraphHTML returns an html representation of og: meta tags.
 func (md *MycoDoc) OpenGraphHTML() string {
-	return ""
+	md.ogFillVars()
+	return strings.Join([]string{
+		ogTag("title", md.hyphaName),
+		ogTag("type", "article"),
+		ogTag("image", md.firstImageURL),
+		ogTag("url", util.URL+"/page/"+md.hyphaName),
+		ogTag("determiner", ""),
+		ogTag("description", htmlTagRe.ReplaceAllString(md.description, "")),
+	}, "\n")
+}
+
+func (md *MycoDoc) ogFillVars() *MycoDoc {
+	foundDesc := false
+	md.firstImageURL = HyphaImageForOG(md.hyphaName)
+	for _, line := range md.ast {
+		switch v := line.contents.(type) {
+		case string:
+			if !foundDesc {
+				md.description = v
+				foundDesc = true
+			}
+		case Img:
+			if len(v.entries) > 0 {
+				md.firstImageURL = v.entries[0].path.String()
+			}
+		}
+	}
+	return md
+}
+
+func ogTag(property, content string) string {
+	return fmt.Sprintf(`<meta property="og:%s" content="%s"/>`, property, content)
 }
 
 /* The rest of this file is currently unused. TODO: use it I guess */
diff --git a/markup/parser.go b/markup/parser.go
index 23887d1..50ff158 100644
--- a/markup/parser.go
+++ b/markup/parser.go
@@ -1,35 +1,24 @@
 package markup
 
-import ()
-
 const maxRecursionLevel = 3
 
-type GemParserState struct {
-	recursionLevel int
-}
-
-func Parse(ast []Line, from, to int, state GemParserState) (html string) {
-	if state.recursionLevel > maxRecursionLevel {
+func Parse(ast []Line, from, to int, recursionLevel int) (html string) {
+	if recursionLevel > maxRecursionLevel {
 		return "Transclusion depth limit"
 	}
 	for _, line := range ast {
 		if line.id >= from && (line.id <= to || to == 0) || line.id == -1 {
 			switch v := line.contents.(type) {
 			case Transclusion:
-				html += Transclude(v, state)
+				html += Transclude(v, recursionLevel)
 			case Img:
 				html += v.ToHtml()
 			case string:
 				html += v
 			default:
-				html += "Unknown"
+				html += "<b class='error'>Unknown element.</b>"
 			}
 		}
 	}
 	return html
 }
-
-func ToHtml(name, text string) string {
-	state := GemParserState{}
-	return Parse(lex(name, text), 0, 0, state)
-}
diff --git a/markup/xclusion.go b/markup/xclusion.go
index b4a4370..a5df6c8 100644
--- a/markup/xclusion.go
+++ b/markup/xclusion.go
@@ -17,14 +17,14 @@ type Transclusion struct {
 }
 
 // Transclude transcludes `xcl` and returns html representation.
-func Transclude(xcl Transclusion, state GemParserState) (html string) {
-	state.recursionLevel++
+func Transclude(xcl Transclusion, recursionLevel int) (html string) {
+	recursionLevel++
 	tmptOk := `<section class="transclusion transclusion_ok">
 	<a class="transclusion__link" href="/page/%s">%s</a>
 	<div class="transclusion__content">%s</div>
 </section>`
 	tmptFailed := `<section class="transclusion transclusion_failed">
-	<p>Failed to transclude <a href="/page/%s">%s</a></p>
+	<p class="error">Hypha <a class="wikilink_new" href="/page/%s">%s</a> does not exist</p>
 </section>`
 	if xcl.from == xclError || xcl.to == xclError || xcl.from > xcl.to {
 		return fmt.Sprintf(tmptFailed, xcl.name, xcl.name)
@@ -34,7 +34,8 @@ func Transclude(xcl Transclusion, state GemParserState) (html string) {
 	if err != nil {
 		return fmt.Sprintf(tmptFailed, xcl.name, xcl.name)
 	}
-	xclText := Parse(lex(xcl.name, rawText), xcl.from, xcl.to, state)
+	md := Doc(xcl.name, rawText)
+	xclText := Parse(md.lex(), xcl.from, xcl.to, recursionLevel)
 	return fmt.Sprintf(tmptOk, xcl.name, xcl.name, binaryHtml+xclText)
 }
 
diff --git a/templates/http_stuff.qtpl b/templates/http_stuff.qtpl
index 9bacf51..3a88e2f 100644
--- a/templates/http_stuff.qtpl
+++ b/templates/http_stuff.qtpl
@@ -1,10 +1,11 @@
-{% func BaseHTML(title, body string) %}
+{% func BaseHTML(title, body string, headElements ...string) %}
 <!doctype html>
 <html>
 	<head>
 		<meta name="viewport" content="width=device-width, initial-scale=1">
 		<link rel="stylesheet" type="text/css" href="/static/common.css">
 		<title>{%s title %}</title>
+		{% for _, el := range headElements %}{%s= el %}{% endfor %}
 	</head>
 	<body>
 		{%s= body %}
diff --git a/templates/http_stuff.qtpl.go b/templates/http_stuff.qtpl.go
index 8fa0096..1e2bd99 100644
--- a/templates/http_stuff.qtpl.go
+++ b/templates/http_stuff.qtpl.go
@@ -18,7 +18,7 @@ var (
 )
 
 //line templates/http_stuff.qtpl:1
-func StreamBaseHTML(qw422016 *qt422016.Writer, title, body string) {
+func StreamBaseHTML(qw422016 *qt422016.Writer, title, body string, headElements ...string) {
 //line templates/http_stuff.qtpl:1
 	qw422016.N().S(`
 <!doctype html>
@@ -31,55 +31,64 @@ func StreamBaseHTML(qw422016 *qt422016.Writer, title, body string) {
 	qw422016.E().S(title)
 //line templates/http_stuff.qtpl:7
 	qw422016.N().S(`</title>
+		`)
+//line templates/http_stuff.qtpl:8
+	for _, el := range headElements {
+//line templates/http_stuff.qtpl:8
+		qw422016.N().S(el)
+//line templates/http_stuff.qtpl:8
+	}
+//line templates/http_stuff.qtpl:8
+	qw422016.N().S(`
 	</head>
 	<body>
 		`)
-//line templates/http_stuff.qtpl:10
+//line templates/http_stuff.qtpl:11
 	qw422016.N().S(body)
-//line templates/http_stuff.qtpl:10
+//line templates/http_stuff.qtpl:11
 	qw422016.N().S(`
 	</body>
 </html>
 `)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
 }
 
-//line templates/http_stuff.qtpl:13
-func WriteBaseHTML(qq422016 qtio422016.Writer, title, body string) {
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
+func WriteBaseHTML(qq422016 qtio422016.Writer, title, body string, headElements ...string) {
+//line templates/http_stuff.qtpl:14
 	qw422016 := qt422016.AcquireWriter(qq422016)
-//line templates/http_stuff.qtpl:13
-	StreamBaseHTML(qw422016, title, body)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
+	StreamBaseHTML(qw422016, title, body, headElements...)
+//line templates/http_stuff.qtpl:14
 	qt422016.ReleaseWriter(qw422016)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
 }
 
-//line templates/http_stuff.qtpl:13
-func BaseHTML(title, body string) string {
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
+func BaseHTML(title, body string, headElements ...string) string {
+//line templates/http_stuff.qtpl:14
 	qb422016 := qt422016.AcquireByteBuffer()
-//line templates/http_stuff.qtpl:13
-	WriteBaseHTML(qb422016, title, body)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
+	WriteBaseHTML(qb422016, title, body, headElements...)
+//line templates/http_stuff.qtpl:14
 	qs422016 := string(qb422016.B)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
 	qt422016.ReleaseByteBuffer(qb422016)
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
 	return qs422016
-//line templates/http_stuff.qtpl:13
+//line templates/http_stuff.qtpl:14
 }
 
-//line templates/http_stuff.qtpl:15
+//line templates/http_stuff.qtpl:16
 func StreamHyphaListHTML(qw422016 *qt422016.Writer, tbody string, pageCount int) {
-//line templates/http_stuff.qtpl:15
+//line templates/http_stuff.qtpl:16
 	qw422016.N().S(`
 <main>
 	<h1>List of hyphae</h1>
 	<p>This wiki has `)
-//line templates/http_stuff.qtpl:18
+//line templates/http_stuff.qtpl:19
 	qw422016.N().D(pageCount)
-//line templates/http_stuff.qtpl:18
+//line templates/http_stuff.qtpl:19
 	qw422016.N().S(` hyphae.</p>
 	<table>
 		<thead>
@@ -90,105 +99,105 @@ func StreamHyphaListHTML(qw422016 *qt422016.Writer, tbody string, pageCount int)
 		</thead>
 		<tbody>
 			`)
-//line templates/http_stuff.qtpl:27
+//line templates/http_stuff.qtpl:28
 	qw422016.N().S(tbody)
-//line templates/http_stuff.qtpl:27
+//line templates/http_stuff.qtpl:28
 	qw422016.N().S(`
 		</tbody>
 	</table>
 </main>
 `)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 }
 
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 func WriteHyphaListHTML(qq422016 qtio422016.Writer, tbody string, pageCount int) {
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	qw422016 := qt422016.AcquireWriter(qq422016)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	StreamHyphaListHTML(qw422016, tbody, pageCount)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	qt422016.ReleaseWriter(qw422016)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 }
 
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 func HyphaListHTML(tbody string, pageCount int) string {
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	qb422016 := qt422016.AcquireByteBuffer()
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	WriteHyphaListHTML(qb422016, tbody, pageCount)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	qs422016 := string(qb422016.B)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	qt422016.ReleaseByteBuffer(qb422016)
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 	return qs422016
-//line templates/http_stuff.qtpl:31
+//line templates/http_stuff.qtpl:32
 }
 
-//line templates/http_stuff.qtpl:33
+//line templates/http_stuff.qtpl:34
 func StreamHyphaListRowHTML(qw422016 *qt422016.Writer, hyphaName, binaryMime string, binaryPresent bool) {
-//line templates/http_stuff.qtpl:33
+//line templates/http_stuff.qtpl:34
 	qw422016.N().S(`
 			<tr>
 				<td><a href="/page/`)
-//line templates/http_stuff.qtpl:35
+//line templates/http_stuff.qtpl:36
 	qw422016.E().S(hyphaName)
-//line templates/http_stuff.qtpl:35
+//line templates/http_stuff.qtpl:36
 	qw422016.N().S(`">`)
-//line templates/http_stuff.qtpl:35
+//line templates/http_stuff.qtpl:36
 	qw422016.E().S(hyphaName)
-//line templates/http_stuff.qtpl:35
+//line templates/http_stuff.qtpl:36
 	qw422016.N().S(`</a></td>
 			`)
-//line templates/http_stuff.qtpl:36
+//line templates/http_stuff.qtpl:37
 	if binaryPresent {
-//line templates/http_stuff.qtpl:36
+//line templates/http_stuff.qtpl:37
 		qw422016.N().S(`
 				<td>`)
-//line templates/http_stuff.qtpl:37
+//line templates/http_stuff.qtpl:38
 		qw422016.E().S(binaryMime)
-//line templates/http_stuff.qtpl:37
+//line templates/http_stuff.qtpl:38
 		qw422016.N().S(`</td>
 			`)
-//line templates/http_stuff.qtpl:38
+//line templates/http_stuff.qtpl:39
 	} else {
-//line templates/http_stuff.qtpl:38
+//line templates/http_stuff.qtpl:39
 		qw422016.N().S(`
 				<td></td>
 			`)
-//line templates/http_stuff.qtpl:40
+//line templates/http_stuff.qtpl:41
 	}
-//line templates/http_stuff.qtpl:40
+//line templates/http_stuff.qtpl:41
 	qw422016.N().S(`
 			</tr>
 `)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 }
 
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 func WriteHyphaListRowHTML(qq422016 qtio422016.Writer, hyphaName, binaryMime string, binaryPresent bool) {
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	qw422016 := qt422016.AcquireWriter(qq422016)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	StreamHyphaListRowHTML(qw422016, hyphaName, binaryMime, binaryPresent)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	qt422016.ReleaseWriter(qw422016)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 }
 
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 func HyphaListRowHTML(hyphaName, binaryMime string, binaryPresent bool) string {
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	qb422016 := qt422016.AcquireByteBuffer()
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	WriteHyphaListRowHTML(qb422016, hyphaName, binaryMime, binaryPresent)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	qs422016 := string(qb422016.B)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	qt422016.ReleaseByteBuffer(qb422016)
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 	return qs422016
-//line templates/http_stuff.qtpl:42
+//line templates/http_stuff.qtpl:43
 }